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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:
Thewindsofchange · 19/07/2026 12:46

Apologies I’ve not rtft
The difference here is in the wording. ‘Splitting the bill 50/50’ is not the same as ‘paying for parents’’. Your op says you and your sister agreed to treat your mum and dad. In that circumstances that means you and your sister paying for them; so you pay for one and your sister pays for the other. Then you pay for your respective meals and those of your dependents etc, if applicable.
if however the agreement with your sister was more loosely worded as ‘shall we just split’ then I can see where she understood that from but, even if I was her, I would not see a 50/50 as fair to you at all. She has to understand that her family costs more. Her family: her responsibility. Considering the bill was reduced for your meal already I think the split is more than fair.

BunnyLake · 19/07/2026 12:49

Calliopespa · 19/07/2026 12:34

Some people have treated the thread as a maths problem, the others treated it as an interpersonal one.

I don't think there is a right or wrong in that, but there is no need to be rude or insulting if others take the different view.

I wonder if the sister has form for being a CF though as she wanted more money to cover her dh and son and discussed it with the mother with such ease.

At its simplest, OP’s £140 was just for the dad.
Sister’s £140 was for herself, her mother, her husband and her son. (If sister had her way).

BlueRedCat · 19/07/2026 12:49

Whenever I go out with my sibling I always pay a greater share as I have more children. The other day I went out with my family of 4, my sibling (without their partner) and their child and our parents. We said we would pay for our parents but obviously I paid much more as there were 4 of us versus
2 of my sibling’s family. my children also ate adult portions vs their child’s small portion. I wouldn’t have dreamed of my sibling subsidising my family! That was us splitting the bill. It definitely didn’t mean 50:50

januaryjanuarydone · 19/07/2026 12:50

Newbie8918 · 19/07/2026 12:34

No but it does mean both sisters usually pay zero. All of those lovely meals for free. Op suggested that the sisters pay this time without being clear but expects sister to pay more to cover her family so sis inevitably comes out worse, no matter what. I’m glad that my family doesn’t work like this but I’m clearly in the minority here!

What do you mean “the sis comes out worse”? Well of course she does if usually her dad pays the bill for her, her DH and her son as their meals will cost more because there are three of them. If the OP had paid exactly half, she comes out worse. I absolutely cannot understand how so many people think it’s unreasonable that the OP pay for her meal and one parent, and her sister’s family pay for their meals and one parent. This thread is completely baffling me!

MissSeventies · 19/07/2026 12:50

Wow, you have fallen into the trap of Mumsnet hair splitting here OP. I don't think you are being U. Obvously it was a misunderstanding between you and your sister and she shouldn't have brought it up to your Mum as it ruins the treat. If you are expected to 'suck up' £35 why can't she. Your intention should have been obvious in how much you paid and she should accepted this and moved on or brought it up to you if she must. For what it is worth this is how we split a treat if we pay for our parents meal as a family, myself and my siblings all have 2 to 3 kids each all attending. An even split would be an unfair burden on my single brother. When parents pay for all of us that is their treat to their children. When we pay for them we are treating them, not them and our siblings and their kids. You are not wrong OP and it was unreasonable of your sister to bring it up.

Flowertopz · 19/07/2026 12:53

If my sister asked me to split the bill to treat our parents id have assumed If it was only the parents and me and my sister id just go 50/50 if she bought her family out to the meal then absolutely not , id have covered half of the parents bill then my share ,why on earth would i pay half a parents ,myself then half her partners and child .

Id be telling my sister to do one and if she got the hump over it then thats a her problem.

Calliopespa · 19/07/2026 12:53

BunnyLake · 19/07/2026 12:49

I wonder if the sister has form for being a CF though as she wanted more money to cover her dh and son and discussed it with the mother with such ease.

At its simplest, OP’s £140 was just for the dad.
Sister’s £140 was for herself, her mother, her husband and her son. (If sister had her way).

Edited

I have been assuming the Dsis has form as I was fairly stunned she raised this with the mother.

Also everything people have said to the op about not quibbling over £35 when the parents have been generous to them in the past applies a fortiori to the Dsis.

But I did notice a comment from a pp who said perhaps the Dsis went to the mum as the OP has form for being difficult to talk to, and I have to say her replies on this thread to people who took time to share a perspective do suggest there might be an element of that.

januaryjanuarydone · 19/07/2026 12:56

Malinia · 19/07/2026 12:00

For all those arguing that the op should have paid 50% of the bill how would you feel if it had not been a meal out but instead had been a holiday?

If the agreement had been to treat the parents to a holiday away would you expect the op to pay 50% of the entire holiday bill, meaning that she was paying for herself and her parents on holiday and the sister was only paying for her immediate family unit to go away on holiday?

Would you think that was fair? because that is an exact analogy.

Yes I like this analogy. If you extrapolate to much higher costs then you really see how unfair it is.
OP have you spoken to your sister and mum since?

SaveMeFromMyBoobs · 19/07/2026 12:57

"Hi sister, mum said there had been some confusion around the bill. From my calculations bill was £X total - £A my bill, £B your family, £C parents bill. As we agreed to split cost of parents 50/50 as a gift I sent you £(half of C) on top of my bill to cover it. If you think I've gone wrong with my maths somewhere please let me know. OP"

If she comes back with splitting the whole bill 50/50 then you can ask why she's expecting you to completely cover your parents when it was supposed to be a joint gift or why shes expecting you to pay for her family.

milveycrohn · 19/07/2026 13:01

I think in cases like this, it's always best to be exact about what you are both paying up front.
ie; I'll be paying for myself, plus half of my joint parents meals.
Of course, this becomes confusing if you share a bottle of wine between you all, so make sure you keep drinks separate.
Also, make sure you add enough for your share of a 'tip'. (if you are adding to the bill.)
In the UK, we tend to add to the bill, but elsewhere, customers still prefer to leave on the table, thoiugh as I carry very little cash, this would not be an option for me.

Yellowchair1 · 19/07/2026 13:04

I 100% agree with you here - why an earth would you split the total bill when you are 1 person v your sis who has 3 people in her fam. It blows my mind people think you should have gone half half. I think the issue is that couples tend to 'forget' they are multiple people, as a single person I try to remind me that my 'unit' is one rather than two people

MauveFatball · 19/07/2026 13:09

KnickerlessFatWoman · 19/07/2026 09:21

But if I pay half, she hasn’t spent anything on my parents’ meals. With a 50/50 split, she and her family just happen to have been there while I treated my parents.

I don’t know how I can make this any simpler.

I totally get where you’re coming from OP, what you paid for was correct and I would have done the same. I don’t understand why others can’t see how unfair splitting the bill in half would have been - you paid ‘your’ share of meal plus half of your parents meals and your sister paid for her family’s meals and the other half of your parents meals….simple!

ScorchedEarthAdjacent · 19/07/2026 13:11

I get it OP. Money is a bit tight for me and in the past when my siblings and I have treated our mum to a meal out, we pay per family and split my mum’s meal between us. My siblings and I each have 2 children but one is a single parent. I wouldn’t expect them to pay the same as other siblings who have partners. Likewise one sibling has very young children who eat off the kids menu which is less. I wouldn’t expect them to pay for 4 adult meals. And then some are better off, some have alcohol, etc. It’s just easier to split by family and then spilt my mum’s cost between us so no one feels they have paid too much.

GertieLawrence · 19/07/2026 13:12

The worst thing about this entire situation, is that because two grown adult sisters cannot communicate or get beyond silly principles, the mother’s memory of her birthday meal out is forever tainted.

And OP has stated that the £35 is neither here nor there to her as she is “fortunate”.

EstoyRobandoSuCasa · 19/07/2026 13:17

GertieLawrence · 19/07/2026 13:12

The worst thing about this entire situation, is that because two grown adult sisters cannot communicate or get beyond silly principles, the mother’s memory of her birthday meal out is forever tainted.

And OP has stated that the £35 is neither here nor there to her as she is “fortunate”.

Edited

I don't think OP has done anything wrong. It was poor form of OP's sister to involve their mother instead of querying the amount with OP.

Brightonbex · 19/07/2026 13:18

God, I’d be embarrassed to start arguing over £35. Just split it equally and move on. It was a family meal for your parents’ birthday. One of the diners was a child, and your BIL wasn’t even drinking, so it’s not like they were taking advantage or expecting you to pay for people eating and drinking excessively!

EstoyRobandoSuCasa · 19/07/2026 13:19

januaryjanuarydone · 19/07/2026 12:50

What do you mean “the sis comes out worse”? Well of course she does if usually her dad pays the bill for her, her DH and her son as their meals will cost more because there are three of them. If the OP had paid exactly half, she comes out worse. I absolutely cannot understand how so many people think it’s unreasonable that the OP pay for her meal and one parent, and her sister’s family pay for their meals and one parent. This thread is completely baffling me!

Me too. Why are people assuming that the sister's husband doesn't have a job and needs his wife or SIL to pay for his meal?

lap90 · 19/07/2026 13:20

I don't think you are being unreasonable at all OP.

If i was your sister and BIL and nephew, i certainly would expect to contribute more than a single adult.

And tbh your sister probably knows deep down she's being a CF which is why she went running to your Mum and couldn't bring it up to you.

Calliopespa · 19/07/2026 13:28

januaryjanuarydone · 19/07/2026 12:56

Yes I like this analogy. If you extrapolate to much higher costs then you really see how unfair it is.
OP have you spoken to your sister and mum since?

I don't disagree but would add that extrapolating to higher costs is changing the context.

I mean what would you say if we backtracked it to a single penny in issue? You'd say "yes, but it is a lot more than a penny at issue."

Iwantanapnow · 19/07/2026 13:33

OP in my family I am in your situation. If my brother and I split the bill we do exactly that and split it equally - even though there are 4 and sometimes 5 on his side. Sometimes they treat me. We are family - we help each other out.
I benefit a lot from being part of a wider family group

Bellyblueboy · 19/07/2026 13:34

Iwantanapnow · 19/07/2026 13:33

OP in my family I am in your situation. If my brother and I split the bill we do exactly that and split it equally - even though there are 4 and sometimes 5 on his side. Sometimes they treat me. We are family - we help each other out.
I benefit a lot from being part of a wider family group

Wow - your brother sounds cheap.

tiantian1005 · 19/07/2026 13:36

Isn't life just too short to be petty about what, 60 quid with your sister? If you really really cant afford it, fine. Otherwise how does 60 change your life?

Crochetandtea · 19/07/2026 13:37

I agree with you op and think you paid the correct amount. The main was removed so that covered your wine.
If your sister queries it with you just say you paid for you and one parent. She’d have to be incredibly tight to expect you to pay the same as her?

tiantian1005 · 19/07/2026 13:39

I mean this is mad. Its family. Over the years our sisters have done so much to help us, for example they came down to look after our daughter when we went to give birth to our second baby which would have cost nearly 1K to have a professional nanny over 4 days period of time, they never mentioned a penny. So if we go out for meal is it mad if I say OH NO we cant cover another 60???

Clarabell77 · 19/07/2026 13:41

Quite cheeky of your sister and brother in law to expect to go halves when there’s 3 of them and one of you.

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