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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:
Trallers · 18/07/2026 13:28

@KnickerlessFatWoman The issue is that there was no clarity regarding what 'treat the parents' meant. It could be interpreted as dad always pays the whole thing so the two sisters will equally share what he would have handed over. Or it could have been interpreted as we'll split the cost of parents meals so they pay nothing.

Unfortunately you both landed on a different one without the other occurring to you as a possibility!

DysmalRadius · 18/07/2026 13:28

my sister and I decided this time it was our turn and we were going to treat him and our mum instead.

This was the deal.

40andnotsofabulous · 18/07/2026 13:29

While I do understand your point, it feels a bit mean. In your situation I would have split the bill 50%. So I can understand your sister’s confusion

this has happened to me multiple times over the years as my sisters had more kids than me- I would never do per head. We just split down the middle!

KnickerlessFatWoman · 18/07/2026 13:29

musicandmen · 18/07/2026 13:24

I would expect 50% if we were splitting the bill. That was the deal

No it wasn’t! Where did I say that?

OP posts:
Nesbi · 18/07/2026 13:29

The sister’s take on this is mad, unless the OP is much wealthier than her and given to acts of enormous generosity. In her position I would have clarified with you - “do you really mean split the bill for everyone, because that would leave you much more out of pocket?!”

KnickerlessFatWoman · 18/07/2026 13:30

You agreed to ‘split the bill’ and from your sisters point of view that meant half each, I think. I would have thought the same.

No I didn’t. Read my OP again.

OP posts:
KnickerlessFatWoman · 18/07/2026 13:30

40andnotsofabulous · 18/07/2026 13:29

While I do understand your point, it feels a bit mean. In your situation I would have split the bill 50%. So I can understand your sister’s confusion

this has happened to me multiple times over the years as my sisters had more kids than me- I would never do per head. We just split down the middle!

But it’s NOT mean to expect one adult with one income to pay for both parents, while two adults with two incomes just pay for themselves?

OP posts:
MammaTo · 18/07/2026 13:31

Obviously there’s been a misunderstanding, but reading your post I would have assumed a 50/50 split of the total bill and not the £70 sorry.

Vaxtable · 18/07/2026 13:31

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?

op agreed to split the parents bill, so she paid hers plus half of parents. Sister paid for her family and half of parents it’s not difficult to understand

ClaredeBear · 18/07/2026 13:32

KnickerlessFatWoman · 18/07/2026 13:04

Well I can do that now, but I have only just found out about the my misunderstanding.

I wouldn’t worry about it. Everyone such a post comes up there will be someone saying it would not have happened to them.

Jk987 · 18/07/2026 13:32

I know what you mean but I think I would have gone halves. Firstly it’s your own young nephew included so you surely wouldn’t mind treating him?

Think of all the times your parents have treated you and you’ve paid nothing? You should think of it as literally splitting the bill paying for individual meals. I’d always want to treat my family and not quibble over a few pounds.

MissIonX · 18/07/2026 13:33

KnickerlessFatWoman · 18/07/2026 13:30

But it’s NOT mean to expect one adult with one income to pay for both parents, while two adults with two incomes just pay for themselves?

You're out for a family meal; you say you're treating your parents... I would take that as a 50:50 split (as would 3 other friends sitting here with me).

The idea you only pay for one parent plus your own when your sister now needs to pay for 4 meals when it was you who suggested treating your parents, seems miserly.

Jk987 · 18/07/2026 13:33

*shouldn’t

ClaredeBear · 18/07/2026 13:34

I understand “split the bill” to mean just that - however, if I was your sister I would have reflected, understood there had been a miscommunication and not said anything. So I think your sister’s been a bit mean here, mentioning to your mum.

MrsPapillon · 18/07/2026 13:35

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.

But if OP had split the whole bill 50/50 her sister wouldn’t have been treating the parents at all! OP would have been paying for herself and BOTH parents while her sister would have just paid for herself and her own child and husband.

lifeturnsonadime · 18/07/2026 13:36

Vaxtable · 18/07/2026 13:31

op agreed to split the parents bill, so she paid hers plus half of parents. Sister paid for her family and half of parents it’s not difficult to understand

sorry disagree, the post said the mum and dad often treat the family (to the family meal) so they (the sisters) decided to treat them instead (to the family meal). That implies 50% each.

If OP wanted to just pay for one parent then she should have clarified.

This is a misunderstanding.

As I said upthread when DH and I come to similar arrangements we aways pay more, in relation to what we consume, because we have less kids on both sides of the family.

We don't quibble over this.

BringMeHome · 18/07/2026 13:38

You both agreed to ‘treat your parents’. That means you pay for yourselves and half of your parents bill each. You didn’t agree to treat your sister, BIL and child.

You’re right.

wtdwtdwtd · 18/07/2026 13:38

I’d message sis and say;

Hi sis, mum mentioned you thought I owed some money from x date? I paid £35 for me and £35 for my half of mum and dad’s share. We are sharing the cost of mum and dad’s meals aren’t we?

it’s frustrating because you have done nothing wrong but now you look like the tight arse because your sis expects you to cover half her family!

Shinyandnew1 · 18/07/2026 13:38

The OP didn’t suggest splitting the bill, she suggested to her sister that they treat their mum and dad.

Happydays777 · 18/07/2026 13:38

Shinyandnew1 · 18/07/2026 13:12

OP should pay
35 for her (and that’s being kind as her mains was taken off)
35 for her mum.

sister/BIL should pay
35 for sister
35 for brother in law
35 for nephew
35 for dad

yes, they are paying more and that’s because there are more of them eating. You shouldn’t be out of pocket because there are three of them and only one of you!

This exactly.

Bristolandlazy · 18/07/2026 13:39

It would make no sense for OP to pay half the bill, she'd be treating her sister's family more than her own parents. Her sister is taking the piss, even if the intention was badly worded when initially discussed surely her sister could see that OP would be getting a very bad deal if they literally paid half each. This is family, not taking advantage of work expenses.

GrumpyPanda · 18/07/2026 13:40

Jk987 · 18/07/2026 13:32

I know what you mean but I think I would have gone halves. Firstly it’s your own young nephew included so you surely wouldn’t mind treating him?

Think of all the times your parents have treated you and you’ve paid nothing? You should think of it as literally splitting the bill paying for individual meals. I’d always want to treat my family and not quibble over a few pounds.

OP can treat her nephew when she takes him out one on one. And why on earth should she treat BIL?

BringMeHome · 18/07/2026 13:40

lifeturnsonadime · 18/07/2026 13:36

sorry disagree, the post said the mum and dad often treat the family (to the family meal) so they (the sisters) decided to treat them instead (to the family meal). That implies 50% each.

If OP wanted to just pay for one parent then she should have clarified.

This is a misunderstanding.

As I said upthread when DH and I come to similar arrangements we aways pay more, in relation to what we consume, because we have less kids on both sides of the family.

We don't quibble over this.

If OP pays 50%, her sister isn’t treating her parents at all. Her sister said she wanted to treat her parents so she needs to pay something for them. OP is right.

DailyEnergyCrisis · 18/07/2026 13:41

YANBU totally CF on their side.

snoopinginstlye · 18/07/2026 13:42

Shinyandnew1 · 18/07/2026 13:04

If your meal was taken off the bill, you should have paid £35! £70 is more than reasonable though.

They shouldn’t have involved your mum in that at all.

i would speak to your sister directly.

totally agree think more than generous to pay your half when they had knocked it off

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