A birthday wish in English opens with "happy birthday" and then adds one more line, and that second line is where the ways to say happy birthday differ. To a friend the second line is a joke or a plan, to a manager it is a wish for the year ahead, and to a child it is a question about cake. The everyday wishes come first, because they fit anyone at all.
Common Ways to Say Happy Birthday in Everyday English
These six wishes fit almost anyone, from a neighbour to a cousin, and each one adds a little to the two words themselves.
Happy birthday: the standard wish at every level, in speech and in writing. It goes with the person’s name and an exclamation mark.
- Happy birthday, Arjun, is that a new bike?
- Happy birthday! I left a small parcel on your desk.
- Oh, it’s today? Happy birthday, I had no idea.
Have a great one: the relaxed second line after "happy birthday", and it fits friends, neighbours, and colleagues you chat with. "One" means "birthday".
- Happy birthday, Sam, have a great one.
- Have a great one, and don’t do any work today.
- Thirty already? Have a great one, mate.
I hope you have a wonderful day: warm and polite, so it fits a card, a message, or a call to anyone at all.
- Happy birthday, Auntie Rose, I hope you have a wonderful day.
- I hope you have a wonderful day with the family.
- I hope you have a wonderful day, and I’ll see you at the weekend.
Enjoy your day: short and friendly, and it fits a shop assistant, a teacher, or a colleague who hears it is your birthday.
- Happy birthday, enjoy your day.
- Enjoy your day, Mrs Kaur, the cake is on the house.
- Go home early and enjoy your day.
All the best on your birthday: neutral and a little formal, and it works for an older relative, a teacher, or a client.
- All the best on your birthday, Mr Osei.
- Happy birthday and all the best on your birthday from everyone at the clinic.
- All the best on your birthday, Grandad, we’ll be over at four.
Wishing you a lovely birthday: a written wish for a card, a note on a gift, or a message to a friend of the family.
- Wishing you a lovely birthday, Nadia, with love from us all.
- Wishing you a lovely birthday and a year full of good news.
- Happy birthday, Tom, wishing you a lovely birthday from the whole team.
Say "happy birthday" first, then add "have a great one" or "I hope you have a wonderful day" to match the person.
Casual Ways to Say Happy Birthday to Friends
Casual wishes are for people who know you well, and they sound quick, warm, and a little playful.
Happy bday: the short written form of "happy birthday" for texts between friends. It is wrong in a card or an email to anyone senior.
- Happy bday, Jess! Party still on for eight?
- Happy bday, you old man.
- Late to the chat, but happy bday, Kemi!
Hope it’s a good one: friendly and relaxed, and it fits a message to a friend or a classmate you like.
- Hope it’s a good one, Dan, cake’s on me at lunch.
- Happy birthday, hope it’s a good one!
- Hope it’s a good one, and text me when you’re free.
Have a blast: a wish for a fun day or a fun party, and it fits friends who are going out to celebrate.
- Have a blast tonight, and send me photos.
- Happy birthday, Mia, have a blast in Lisbon.
- Have a blast, you deserve a night off.
It’s your day: a casual line that means "do what you want today", and it goes with a plan or an offer.
- Happy birthday, it’s your day, so you pick the film.
- It’s your day, I’ll do the washing up.
- Relax, it’s your day, the kids are with me.
Cheers to you: the words of a toast, and they fit a drink with friends or a short message on the day.
- Cheers to you, Leo, happy birthday!
- Raise your glass, cheers to you and another good year.
- Cheers to you, mate, thirty looks fine on you.
Keep "happy bday" and "have a blast" for friends your own age, and write "happy birthday" in full for everyone else.
Formal Ways to Say Happy Birthday at Work
A work wish fits a colleague, a manager, or a client, and it stays short, names the person, and never mentions age.
Happy birthday, Ms Adams: "happy birthday" with a title and surname is the standard formal wish for a manager or a client you do not know well.
- Happy birthday, Ms Adams, I hope you have a pleasant day.
- Happy birthday, Dr Okafor, from all of us in reception.
- Happy birthday, Mr Petrov, we hope the year ahead goes well.
Wishing you all the best on your special day: the polite written wish for a card that the whole office signs.
- Wishing you all the best on your special day, Priya.
- Wishing you all the best on your special day and every success in the year ahead.
- Happy birthday, and wishing you all the best on your special day from the finance team.
Best wishes on your birthday: neutral and formal, and it fits an email to a client or a note to a senior colleague.
- Best wishes on your birthday, Mr Chen, from everyone at Northfield.
- Best wishes on your birthday and thank you for your support this year.
- Happy birthday, Professor Grant, best wishes on your birthday from the whole department.
I hope the year ahead brings you every success: a very formal second line for a boss, a client, or a business partner.
- Happy birthday, Ms Adams, I hope the year ahead brings you every success.
- I hope the year ahead brings you every success, both at work and at home.
- Many happy returns, and I hope the year ahead brings you every success.
Many happy returns: the traditional British wish, and it means "I hope you have many more birthdays". It fits a senior colleague or an older client.
- Many happy returns, Mrs Ali.
- Many happy returns of the day, Sir Charles.
- Happy birthday and many happy returns, from all of us on the board.
"Congratulations" is the wish for a wedding, a new job, or an exam result, and it sounds translated on a birthday.
- Congratulations on your birthday, Ms Adams. ❌
A birthday is not an achievement in English, so the wish is "happy birthday" plus a polite second line.
- Happy birthday, Ms Adams, I hope you have a lovely day. ✅
"Happy bday" belongs to friends, and it looks careless in a message to someone senior.
- Hey, Ms Adams, happy bday!! ❌
A wish to a manager uses the full words and a title, with one exclamation mark at most.
- Happy birthday, Ms Adams, I hope the day goes well. ✅
Every birthday wish on this page belongs to one of five levels.
| Level | Wishes | Who it fits |
|---|---|---|
| Slang | Happy bday, HBD, have a blast | Close friends your own age |
| Casual | Have a great one, hope it’s a good one, it’s your day | Friends, family, relaxed colleagues |
| Neutral | Happy birthday, enjoy your day, I hope you have a wonderful day | Anyone you know by name |
| Formal | Best wishes on your birthday, happy birthday with a title | Managers, clients, older people |
| Very formal | Many happy returns, I hope the year ahead brings you every success | Senior clients, ceremonies, cards from a company |
Write "happy birthday" with a title and surname for a client, and add "best wishes" rather than a joke.
Ways to Say Happy Birthday in an Email
An email wish goes in the first line after the greeting, and the second line of the email returns to work or to a plan.
Hi Sara, happy birthday!: the standard email wish to a colleague you know by first name, with the greeting and the wish on one line.
- Hi Sara, happy birthday! The team has left something on your desk.
- Hi Sara, happy birthday! No meetings for you this afternoon.
- Hi Sara, happy birthday! Lunch is on us at one.
Dear Mr Chen, happy birthday from all of us at Northfield: the formal email wish to a client, with the company named so the wish reads as an official one.
- Dear Mr Chen, happy birthday from all of us at Northfield, we hope you have a pleasant day.
- Dear Mr Chen, happy birthday from all of us at Northfield, and thank you for another year of working together.
- Dear Mr Chen, happy birthday from all of us at Northfield, please accept our best wishes.
Warm birthday wishes: a short written line that fits the end of an email as well as the start, and it works for a client or a colleague.
- Warm birthday wishes, Tom, from the whole floor.
- Happy birthday, Ms Adams, warm birthday wishes from the London office.
- Warm birthday wishes and see you at Thursday’s meeting.
I hope you’re taking the day off: a friendly second line for a colleague, and it turns the wish into a small joke about work.
- Happy birthday, Raj, I hope you’re taking the day off.
- I hope you’re taking the day off, or at least leaving at five.
- Happy birthday! I hope you’re taking the day off and eating cake.
"Happy birthday" in an email needs no capital letter on "birthday", because the wish is two ordinary words.
- Hi Sara, Happy Birthday! I hope you have a good day. ❌
Capitals belong to a card front or a banner, and in a sentence the wish is written in lower case.
- Hi Sara, happy birthday! I hope you have a good day. ✅
Put the wish in the first line of the email and the work in the second, so the wish does not read as a favour.
Ways to Say Happy Birthday in a Card
A card wish is written by hand, so it is short, it names the person, and it ends with "love" or "best wishes" and your name.
Wishing you a very happy birthday: the most common written wish in a card, and it fits family, friends, and colleagues alike.
- Wishing you a very happy birthday, Grandma, with all our love.
- Wishing you a very happy birthday and a wonderful year.
- To Ben, wishing you a very happy birthday, from Aunt Jo.
Have a wonderful birthday: warm and neutral, and it fits a card to anyone you like but do not know closely.
- Have a wonderful birthday, Nadia, and enjoy every minute.
- Have a wonderful birthday, with best wishes from the whole street.
- Dear Mr Lewis, have a wonderful birthday.
Thinking of you on your birthday: a card line for someone far away, or for someone who is unwell or going through a hard time.
- Thinking of you on your birthday, Mum, wish I could be there.
- Thinking of you on your birthday, and sending love from all of us.
- Thinking of you on your birthday, Dad, see you next month.
Here’s to another great year: a card line that looks forward, and it fits a friend or a relative of any age.
- Happy birthday, Omar, here’s to another great year.
- Here’s to another great year of walks, coffee, and bad jokes.
- Here’s to another great year, with love from Ella and the boys.
Write one wish, one personal line, and your name, because a card with three wishes reads as a printed one.
Ways to Say Happy Birthday in a Text
A text wish is short, and emojis and exclamation marks replace the voice you would use in person.
HBD: the letters of "happy birthday", used in a quick text or a chat between friends. It reads as lazy to anyone outside your friend group.
- HBD, Marco! Drinks later?
- HBD!! Cake at mine at seven.
- Sorry for the late text, HBD, Jay.
Happy birthday, hope you’re having a good one: the full text wish for a friend, and the second half asks about the day as it happens.
- Happy birthday, hope you’re having a good one!
- Happy birthday, hope you’re having a good one, call me when you’re free.
- Happy birthday, hope you’re having a good one, Lucy, what did you get?
Big birthday hugs: a warm text for a close friend or a relative, and it fits when you cannot be there in person.
- Big birthday hugs, Sofia, miss you.
- Happy birthday! Big birthday hugs from Manchester.
- Big birthday hugs to the best sister in the world.
Keep a text wish to one line, and send it in the morning so the person reads it before the day gets busy.
Ways to Say Happy Birthday to a Partner
A wish to a partner is personal, so it names something you love about the person or a plan for the two of you.
Happy birthday, my love: the standard wish between partners, and it fits a card, a text, or the first words in the morning.
- Happy birthday, my love, breakfast is on its way up.
- Happy birthday, my love, this year is going to be a good one.
- Happy birthday, my love, open the small box first.
I’m so lucky to have you: a warm second line for a partner, and it says more than any gift.
- Happy birthday, Dan, I’m so lucky to have you.
- I’m so lucky to have you, and I hope today is as good as you are.
- Every year with you is better, I’m so lucky to have you.
Here’s to another year together: a toast line for a partner, and it fits dinner out or a card with a plan inside.
- Happy birthday, Anna, here’s to another year together.
- Here’s to another year together, and to Italy in June.
- Here’s to another year together, with all my love.
Happy birthday to my favourite person: playful and sweet, and it fits a text or a message on the day.
- Happy birthday to my favourite person, see you at six.
- Happy birthday to my favourite person, I’ve booked the table.
- Happy birthday to my favourite person in the whole world.
Name one real thing about the person, because a partner reads a general wish as a card from a shop.
Ways to Say Happy Birthday to a Parent
A wish to a parent thanks as well as wishes, and it fits a card, a call, or a hug at the door.
Happy birthday, Mum: the everyday wish, with "Mum" or "Dad" instead of a name, and it goes with a hug or a call.
- Happy birthday, Mum, we’re taking you out tonight.
- Happy birthday, Mum, I hope Dad made you breakfast.
- Happy birthday, Mum, love you.
Thank you for everything you do: the second line that fits a parent on any birthday, and it means more than a long list.
- Happy birthday, Dad, thank you for everything you do.
- Thank you for everything you do, and enjoy a day with nothing to do.
- Happy birthday, Mum, thank you for everything you do for us.
You deserve a day off: a warm line for a parent who works hard, and it goes with an offer to cook or to babysit.
- Happy birthday, Mum, you deserve a day off, so I’m cooking.
- You deserve a day off, Dad, sit down and open your presents.
- You deserve a day off, and we’ve booked the whole afternoon.
To the best dad in the world: a card line for a father, and "mum" replaces "dad" in the same line for a mother.
- To the best dad in the world, happy birthday from all three of us.
- To the best dad in the world, have a great day.
- To the best dad in the world, with love, Sam.
Add a thank-you to a parent’s birthday wish, because the wish alone is what everyone else says.
Ways to Say Happy Birthday to a Child
A wish to a child names the age, asks about the party, and sounds excited.
Happy birthday, big boy: an excited wish for a small child up to about seven, and "big girl" is the same wish for a girl.
- Happy birthday, big boy, are you five today?
- Happy birthday, big girl, look at all those balloons!
- Happy birthday, big boy, Grandad has a present for you.
You’re seven today: naming the age is a wish in itself for a child, and the child is proud to hear the number.
- You’re seven today, Ava, that’s a whole hand and two fingers.
- Wow, you’re seven today! Happy birthday!
- You’re seven today, so you get seven candles.
Have a fun day: short enough for a child, and it fits a teacher, a neighbour, or a friend’s parent.
- Happy birthday, Noah, have a fun day.
- Have a fun day, and save me some cake.
- Have a fun day at the party, Lily.
Happy birthday, sweetheart: a soft wish from a parent or a grandparent to a child, in person or in a card.
- Happy birthday, sweetheart, come and open your presents.
- Happy birthday, sweetheart, we love you very much.
- Happy birthday, sweetheart, did the balloons wake you?
Say the age out loud when you wish a child a happy birthday, because the number is the part the child enjoys most.
Ways to Say Happy Birthday to a Best Friend
A wish to a best friend is warm and honest, and it fits a joke, a memory, or a plain "love you".
Happy birthday, bestie: the everyday wish between best friends, in a text or out loud. "Bestie" is casual and mostly young.
- Happy birthday, bestie, drinks at eight!
- Happy birthday, bestie, love you loads.
- Happy birthday, bestie, I’ve got your present in my bag.
I’m so glad you were born: a warm line that fits a best friend or a partner, and it sounds sweet rather than funny.
- Happy birthday, Amy, I’m so glad you were born.
- I’m so glad you were born, and I’m even more glad we met.
- I’m so glad you were born, you idiot, happy birthday.
Here’s to many more years of friendship: a toast line for a best friend, and it fits a card or a speech at the party.
- Here’s to many more years of friendship, Ravi, happy birthday.
- Here’s to many more years of friendship and terrible films.
- Happy birthday, here’s to many more years of friendship.
Love you, happy birthday: the shortest honest wish, and it fits a best friend, a sibling, or a partner.
- Love you, happy birthday, see you tonight.
- Love you, happy birthday, Nina!
- Love you, happy birthday, sorry I can’t be there.
Tell a best friend one true thing on their birthday, and let the joke come after the wish.
Ways to Say Happy Birthday on a Milestone Birthday
A milestone birthday ends in a zero or marks a legal age, and the wish names the number with pride.
Happy 18th, welcome to adult life: the wish for an eighteenth birthday, the age of adulthood in Britain and most other countries, and it fits family and friends.
- Happy 18th, welcome to adult life, Sam, the first vote is yours.
- Happy 18th, welcome to adult life, and the first coffee is on you.
- Happy 18th, welcome to adult life, we’re so proud of you.
Welcome to your thirties: the wish for a thirtieth birthday, and it fits friends and siblings who are already past thirty.
- Happy birthday and welcome to your thirties, Jess.
- Welcome to your thirties, they’re better than the twenties.
- Welcome to your thirties, mate, how does it feel?
Life begins at forty: an old saying that says the best years start at forty, and it turns the number into a compliment.
- Happy 40th, Dad, life begins at forty.
- Life begins at forty, so this is your first birthday.
- They say life begins at forty, and you look ready for it.
Happy 50th, half a century: the wish for a fiftieth birthday, and "half a century" is the joke friends make about the number.
- Happy 50th, half a century and still the fastest runner in the family.
- Happy 50th, half a century, Mum, here’s to the next fifty.
- Happy 50th, half a century, we’ve booked the restaurant.
Happy 60th, here’s to the next chapter: the wish for a sixtieth birthday, and "the next chapter" means the years after work.
- Happy 60th, here’s to the next chapter, Grandad.
- Happy 60th, here’s to the next chapter, and to more time in the garden.
- Happy birthday, Auntie Rose, happy 60th, here’s to the next chapter.
Name the number on a milestone birthday, and turn it into a compliment rather than a joke about age.
Ways to Say Happy Belated Birthday
A late wish says sorry in a light way and still wishes well, and "belated" means "late".
Happy belated birthday: the standard late wish, and it fits a text, a card, or a call up to a few weeks after the day.
- Happy belated birthday, Kwame, I only saw the photos today.
- Happy belated birthday! Did you have a good one?
- Happy belated birthday, Mrs Ali, the card is in the post.
Belated happy birthday: the same wish with the words in a different order, and both orders are correct. This order is a little more common in British English.
- Belated happy birthday, Priya, sorry I missed it.
- Belated happy birthday from all of us in the office.
- Belated happy birthday, and I still owe you a drink.
Sorry I missed your birthday: an apology first, and the wish comes after it. It fits a close friend or a relative.
- Sorry I missed your birthday, Tom, happy belated.
- Sorry I missed your birthday, I was on a night shift all week.
- Sorry I missed your birthday, let me take you out this weekend.
Better late than never: a saying that means a late wish is still worth sending, and it goes with a smile.
- Happy belated birthday, and better late than never, right?
- Better late than never, happy birthday for last Tuesday.
- Better late than never, I’ve got your present in the car.
Send a late wish with a short sorry and a plan, because a long apology makes the person feel worse than the missed day did.
Ways to Say Happy Birthday to a Group
A group wish names everyone at once, and it fits a family message, a work chat, or a card from a team.
Happy birthday from all of us: the standard wish from a group, and it fits a card from an office, a class, or a family.
- Happy birthday from all of us, Nadia.
- Happy birthday from all of us on the third floor.
- Happy birthday from all of us, Grandma, with love.
Happy birthday to you both: the wish for twins, or for two people who share a birthday.
- Happy birthday to you both, one cake or two?
- Happy birthday to you both, Ella and Jake.
- Happy birthday to you both, from the whole street.
Three cheers for the birthday girl: the words that start a cheer at a party, and "birthday boy" replaces "birthday girl" for a man.
- Three cheers for the birthday girl, hip hip, hooray!
- Everybody, three cheers for the birthday boy.
- Three cheers for the birthday girl, and then cake.
Write "from all of us" on a group card, and let one person sign for the whole team.
Regional Ways to Say Happy Birthday in English
English-speaking countries each keep a birthday wish or two of their own, and the words after "happy birthday" change with the country.
British Ways to Say Happy Birthday
Many happy returns of the day: the full form of the traditional British wish, now heard mostly from older speakers and in formal cards.
- Many happy returns of the day, Mr Whitmore.
- Many happy returns of the day, Gran, from all the grandchildren.
- Many happy returns of the day, and enjoy the tea.
Happy birthday, mate: the British and Australian casual wish between friends, with "mate" for a friend of any age.
- Happy birthday, mate, pint later?
- Happy birthday, mate, forty suits you.
- Happy birthday, mate, sorry I can’t make it tonight.
Have a lovely day: the British neutral wish, and "lovely" is the word that marks it as British.
- Happy birthday, Claire, have a lovely day.
- Have a lovely day, love, and don’t lift a finger.
- Have a lovely day, Mrs Kaur, from all at the surgery.
American Ways to Say Happy Birthday
Happy birthday, buddy: the American casual wish between male friends, and "buddy" also fits a small boy.
- Happy birthday, buddy, game’s on at seven.
- Happy birthday, buddy, how old are you now, five?
- Happy birthday, buddy, cake’s in the break room.
Hope you have an awesome birthday: "awesome" marks the wish as American, and it fits friends and younger colleagues.
- Hope you have an awesome birthday, Tyler!
- Hope you have an awesome birthday, and eat a lot of cake.
- Hope you have an awesome birthday, see you at the game.
Australian and Irish Ways to Say Happy Birthday
Have a ripper birthday: the Australian casual wish, and "ripper" means "great". It fits friends and family.
- Have a ripper birthday, Liam, beers at the beach later.
- Have a ripper birthday, mate!
- Have a ripper birthday, and no work tomorrow.
Hope you have a grand day: the Irish casual wish, and "grand" means "fine" or "great" in Irish English.
- Happy birthday, Niamh, hope you have a grand day.
- Hope you have a grand day, and we’ll see you at the pub.
- Hope you have a grand day, Sean, love from all in Cork.
Say "many happy returns" in Britain, "buddy" in America, "ripper" in Australia, and "grand" in Ireland, and say "happy birthday" everywhere else.
Funny Ways to Say Happy Birthday
Funny wishes are for close friends and family who laugh at jokes about age, and each one plays on the number of years.
Another year older, another year wiser: a gentle joke that turns age into a compliment, and it fits a sibling or a friend.
- Happy birthday, Dan, another year older, another year wiser.
- Another year older, another year wiser, or at least older.
- Another year older, another year wiser, and still bad at cards.
Happy birthday, you’re not old, you’re vintage: a joke for a friend over forty, and "vintage" means old and valuable at once.
- Happy birthday, you’re not old, you’re vintage.
- Don’t worry, Mum, you’re not old, you’re vintage.
- You’re not old, you’re vintage, like that jacket you never throw away.
Another trip around the sun: a playful way to say "another year", and it fits a text or a card to a friend.
- Happy birthday, Amy, another trip around the sun done.
- Another trip around the sun, and you still look twenty-five.
- Congratulations on another trip around the sun!
Happy birthday, don’t count the candles: a joke about a cake with too many candles, and it fits a friend or a parent who laughs at their age.
- Happy birthday, don’t count the candles, we ran out of room.
- Happy birthday, don’t count the candles, count the presents.
- Happy birthday, don’t count the candles, the fire brigade is on standby.
Save the age jokes for people who make them first, because a joke about age to a colleague reads as an insult.
How Do You Reply When Someone Says Happy Birthday?
A birthday wish is a gift in words, so the reply thanks the person, and a friend gets one extra line about the day.
Thank you: the reply at every level, and it fits a boss, a stranger, or a friend. Add the name for a warmer form.
- Happy birthday, Ms Adams. Thank you, that’s kind of you.
- Happy birthday! Thank you, Priya.
- Many happy returns. Thank you very much.
Thanks so much: the warm casual reply, and it fits friends, family, and colleagues you know.
- Happy birthday, Sam! Thanks so much, I didn’t think anyone knew.
- Have a great one! Thanks so much, mate.
- Happy bday! Thanks so much, see you tonight.
Thanks for remembering: the reply to a wish from someone who did not have to send one, and it says the wish was a surprise.
- Happy belated birthday! Thanks for remembering, that means a lot.
- Happy birthday, Tom. Thanks for remembering, Mrs Ali.
- Thanks for remembering, I’d almost forgotten myself.
I’m having a lovely day: the reply to "I hope you have a good day", and it answers the wish with news.
- Hope it’s a good one! I’m having a lovely day, thanks.
- Happy birthday, enjoy your day. I’m having a lovely day so far.
- I’m having a lovely day, the kids made breakfast.
That’s so sweet of you: the reply to a card, a gift, or a long message, and it fits a friend or a relative.
- Happy birthday, we love you! That’s so sweet of you, thank you.
- Wishing you a very happy birthday. That’s so sweet of you, Auntie Jo.
- That’s so sweet of you, I’ll keep the card.
Reply with "thank you" and the person’s name, and give a friend one line about the day before you move on to other news.
More Everyday English Phrases
- Other Ways to Say Congratulations
- Other Ways to Say Good Luck
- Other Ways to Say Best Wishes
- Other Ways to Say Get Well Soon
FAQs
More than seventy wishes are in everyday use, and new ones appear every year in texts and on cards. The set most speakers rely on is small: "happy birthday", "have a great one", "I hope you have a wonderful day", "many happy returns", and "happy belated birthday". Every other wish adds a level, a relationship, or a joke to one of those five.
"Have a great one", "many happy returns", and "wishing you a wonderful day" are the three most common replacements, and each one works on its own. In speech, "happy birthday" comes first and the replacement follows as the second line. In a card, the replacement can stand alone under the printed words.
"Another year older, another year wiser" and "another trip around the sun" are the two safest funny wishes, because they joke about time rather than about the person. "You’re not old, you’re vintage" fits a friend over forty who laughs at their age. Keep every age joke away from a colleague or a client.
"Happy birthday, Ms Adams, I hope you have a pleasant day" is the standard formal wish, with a title and a surname. "Best wishes on your birthday" and "many happy returns" are the two formal replacements. A formal wish stays short, never mentions age, and never uses "bday" or "HBD".
"Many happy returns" means "I hope this day returns many more times", so it is a wish for a long life. The full form is "many happy returns of the day". It is British, polite, and a little old-fashioned, and it is common on cards and among older speakers.
Yes, a late wish is welcome up to a few weeks after the day, and "happy belated birthday" is the standard form. Add a short sorry and a plan, such as a coffee or a call, rather than a long excuse. After a month, the wish still fits, but it reads better with a reason, such as a trip or an illness.
"Dear Mr Chen, happy birthday from all of us at Northfield, we hope you have a pleasant day" is the standard client message. Name the company, keep the message to two lines, and sign with your name and role. Leave out age, jokes, and any request for work.
"Thank you" is the reply at every level, and the person’s name makes it warmer. To a friend, add one line about the day, such as "I’m having a lovely day" or "the kids made breakfast". "Thanks for remembering" is the reply to a wish from someone who did not have to send one.
