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AIBU?

Share your dilemmas and get honest opinions from other Mumsnetters.

Birthday bill split

1000 replies

KnickerlessFatWoman · 18/07/2026 12:55

Last weekend was my mother’s birthday, so we - that’s me, my parents, sister and BIL and their 12 year-old son - went for Sunday lunch. Unfortunately the food wasn’t great, and they ended up taking my main off the bill.

My dad is someone who always wants to treat everyone, so my sister and I decided this time it was our turn and we were going to treat him and our mum instead. When the bill came, BIL asked if we could split it over two cards, but they said they could only take one payment. He paid and I said I’d transfer my share. For the sake of keeping the maths simple on this thread, let’s say the bill was £210, or £35 per head.

Both BIL and sister are crap at responding to messages, so it took me until midweek to get the bank details. I sent over £70 to cover me and one of my parents.

I heard nothing in response, but I was chatting to my mum earlier and she said “Oh, by the way, Katie said you got the money wrong - it was £210 and you only sent £70”. I said no, that was right - my meal and one other. She said, “Ohhh… I think she thought you were splitting it”. I laughed and said, “No, we said we’d treat you and Dad. I didn’t say I’d pay for three meals!”

I don’t really know why my sister couldn’t just have messaged me instead of talking to our mother about it, but that’s not really the issue. Surely she and BIL don’t expect me to pay half the bill? By treating our parents, I meant exactly that - not that I’d pay for them both while my sister just paid for her own family (which is what this amounts to). There are three of them and one of me. If I pay half the bill, sister and BIL have only covered themselves and their child - there’s no “treating” anyone at all.

AIBU for thinking £70 was my share and paying just that?

OP posts:
elessar · 18/07/2026 14:46

Bit of a dick move I think for your sister to bitch to your mum about this, without even talking to you about it first.

Do you have a good relationship normally?

I think on balance you’re in the right here, although I suspect it’s slightly less clean cut in reality - your BIL and nephew wouldn’t have been drinking which skews the PP costs a little bit.

But the principle absolutely stands - it makes sense for you to cover your share and for half the cost of your parents, not to subsidise your sister’s family of 3.

Tabarnak · 18/07/2026 14:48

Just explain your logic )which is sound) to your DSis.

It was really crass and graceless of her to share this with your Mum. ‘Treating people’ does not mean involving them in negotiations over the bill.

OneLimePombear · 18/07/2026 14:52

Tabarnak · 18/07/2026 14:48

Just explain your logic )which is sound) to your DSis.

It was really crass and graceless of her to share this with your Mum. ‘Treating people’ does not mean involving them in negotiations over the bill.

I think I’d send a text or WhatsApp message to both of them explaining your calculation, double checking you have your figures are right and then not engage in any further communication about it and also try not to think about it.

Mclaren10 · 18/07/2026 14:53

I think its crossed wires.

You paid for yourself and treated one parent - absolutely fine.

Normally your dad pays for everything..so he would paid 210.

Your sis thinks splitting it is paying 105 each. Instead of 0.

Uanbu to not do that.

You pay for yourself plus a parent.
Sis bil nephew pays for themselves plus a parent.
Don't think sis thought that through when offering to treat the parents.

BunnyLake · 18/07/2026 14:53

SpottyPyjama · 18/07/2026 13:12

I’m with your sister. The treat was a meal out with the whole family, so if you agreed to split the treat 50/50 you pay half of what a meal for the whole family costs.

It seems like there was a misunderstanding, but you don’t have some moral high ground here or the automatic right to claim your sister was wrong.

The agreement was for each sister to treat one parent apiece. Suppose sister had six kids, would op have to cover half of them? It’s very simple if each sister knows they’re paying for a parent each and themselves. Any surplus family members are covered by that sister’s side.

Always best to have a clear outline of what’s expected beforehand though. I have a sister and I wouldn’t expect her to contribute to my own family going and neither would she vice versa.

Mclaren10 · 18/07/2026 14:54

Tabarnak · 18/07/2026 14:48

Just explain your logic )which is sound) to your DSis.

It was really crass and graceless of her to share this with your Mum. ‘Treating people’ does not mean involving them in negotiations over the bill.

Agree, it's almost like expecting the parents to make up the difference then...definitely shouldn't have raised it with them.

Birdsongsinging · 18/07/2026 14:54

The 12 year olds share shouldn’t be the same as wine drinking adults.

KnickerlessFatWoman · 18/07/2026 14:55

Birdsongsinging · 18/07/2026 14:54

The 12 year olds share shouldn’t be the same as wine drinking adults.

I took this into consideration by still paying two full shares despite my main being taken off the bill.

OP posts:
QuickPinkFox · 18/07/2026 14:56

lifeturnsonadime · 18/07/2026 13:06

Sorry I misunderstood.

However in my mind if both siblings have agreed to treat parents by splitting the bill then, unless otherwise agreed, then I would think 50% of bill each regardless of the fact that there are are more on their side of the family.

This happens frequently for me / dh as we have less kids than our siblings on both sides. We don't ask the other families to pay more we just split equally.

I disagree with this, and think yanbu op!

this happened to me, me and my sister and her DH agreed we would treat our dad to dinner out for dinner for his birthday. Then when the bill came my sister and her DH paid half, leaving half for me to pay. I didn’t make a fuss infront of my dad but…that just means I treated my dad, not my sis! I think sometimes people who often or always go out as a couple seem to forget they are not one person…

KnickerlessFatWoman · 18/07/2026 14:57

TheCurious0range · 18/07/2026 14:41

This should've been 50/50 because it wasn't about covering your plate, it was covering half each of what your parents usually pay , the treat was to them as they usually pick up the tab

But why should that treat cost me more than it does my sister and BIL?

OP posts:
WWomble · 18/07/2026 14:58

I’m with you OP.

But I think you need to message her - written explanations are harder to misunderstand and explain your calculations. If you split 50/50 she is not actually covering your parents’ meals but if you make it a price per head and each cover an additional ‘head’ then you both contribute equally to your parents’ share.

Good luck

KnickerlessFatWoman · 18/07/2026 14:59

Angelyogini · 18/07/2026 14:29

well op, i guess you managed to upset all your family, involving the parents you tried to treat.
All that for 35 quid - you should have just got over it.

Calm down 🙄🙄

I literally only found out there was an issue three hours ago. No one is sobbing or threatening to cut contact. There’s no need for this “upsetting all the family” drama.

OP posts:
AppropriateAdult · 18/07/2026 15:00

It sounds like a misunderstanding, but what’s unforgivable is your sister raising it with your mum at all - it’s incredibly crass to ‘treat’ somebody and then complain that you feel hard done by afterwards Confused

MustTryHarderAndHarder · 18/07/2026 15:01

KnickerlessFatWoman · 18/07/2026 14:35

But surely she hasn’t clarified it either?

Not sure why you are getting such a hard time on here.

You are obviously in the right.

I think that the people disagreeing with you aren't logical.

Andepeda · 18/07/2026 15:01

I can't believe your sister dragged your mum into it.

Your parents usually pay for three of them and only one of you.

You're losing out big time OP.

allthingsinmoderation · 18/07/2026 15:02

lifeturnsonadime · 18/07/2026 12:58

I think DSis is right, if the intention was to split the bill in half then it would be £105 each.

Did you think your parents were paying for themselves?

I think the intention was to pay for their own food and split the parents bill between them so as to treat their parents.

BunnyLake · 18/07/2026 15:03

TheCurious0range · 18/07/2026 14:41

This should've been 50/50 because it wasn't about covering your plate, it was covering half each of what your parents usually pay , the treat was to them as they usually pick up the tab

It wasn’t covering half each of what they usually pay it was paying for the parents as a treat so the parents didn’t have to pay this time. That’s not the same thing.

Disasterclass · 18/07/2026 15:03

DB and I take our DM for lunch every year on her birthday. The years that my DD comes I pay more, the years she doesn’t we split 50-50. I wouldn’t dream of expecting him to pay for part of DD’s meal as well. We’re not always exact but it’s the principle that as the sibling with a child I expect to pay more. We didn’t agree it in advance either, the first year we did it I paid first and made sure I paid the bigger share, since I’m not a CF.

There may have been a misunderstanding but the sister should have realised that she should pay more for her family that you.

BillieWiper · 18/07/2026 15:05

I don't think it was clear you'd only pay for one parent if you said you wanted to treat both of them? Surely you paid both theirs plus yours?
Or maybe yours doesn't exist if it was removed from the bill?

allthingsinmoderation · 18/07/2026 15:06

i think this is a misunderstanding.
Your idea of treat your parents was to pay for yourself and split your parents bill between you .
Your sisters idea of "treat your parents" was to pay half of the entire bill each ..

BunnyLake · 18/07/2026 15:06

allthingsinmoderation · 18/07/2026 15:02

I think the intention was to pay for their own food and split the parents bill between them so as to treat their parents.

Why can’t other posters understand this?

If sister’s family was made up ten people would posters expect solo OP to cover for them?

The mistake was not being clear with your sister as she sounds a bit dim.

Horses7 · 18/07/2026 15:06

Your sister should pay more of the bill - you should pay for yourself and 1 parent plus tip of course.
Treating your parents doesn’t mean you treat half the bill for your sister’s family

BunnyLake · 18/07/2026 15:08

allthingsinmoderation · 18/07/2026 15:06

i think this is a misunderstanding.
Your idea of treat your parents was to pay for yourself and split your parents bill between you .
Your sisters idea of "treat your parents" was to pay half of the entire bill each ..

Which is completely cheeky if your party is bigger than a single sibling going. The sister is either dim or a cf.

Birdsongsinging · 18/07/2026 15:09

I guess it depends how you normally do things if you weren’t treating your parents. Would you all pay your own according to exactly what you have?

it is all sounding a bit like I had this and that money got taken off and they had this. I wouldn’t be wanting the refund for my share that they took off the bill.

I do see what you mean about them just paying for their own but think that is just what happens- you win some you lose some!

TheCurious0range · 18/07/2026 15:09

KnickerlessFatWoman · 18/07/2026 14:57

But why should that treat cost me more than it does my sister and BIL?

It doesn't it cost you and your sister whose parents they are, the same, say you wanted to buy him a painting for his birthday, you'd pay 50/50, it's no different, the treat here isn't about individual meals, it's about your parents having their whole family together for a meal out and time shared, without them paying for it. If your family dynamic was each family pays for themselves I'd see your point more, but it isn't, your dad pays for everyone.

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