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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:
MrsJeanLuc · 18/07/2026 14:30

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?

No!

It's clear enough. OP expected to pay for herself and one of the parents.
Sis & BIL can pay for themselves and one of the parents.

Perfectly reasonable.
More than reasonable actually, because if op had paid for her actual meal (rather than a per head split of the whole bill) it would have been less, as her main was discounted.

MyCrushWithEyeliner · 18/07/2026 14:30

Blondiebeachbabe · 18/07/2026 14:20

You paid the right amount.

If you paid £105 as suggested, you would have paid for yours AND both parents, meaning that your sister paid for herself, husband and child - meaning that she had treated no one.

Surely she can't be that thick?

Maybe she’s pretending to be thick to get out of paying her share

Angelyogini · 18/07/2026 14:30

And one more thing. OP is great at typing here "treating the parent". How is it both mom and sister got confused in real life?

TheOnlyLivingBoyInNewCross · 18/07/2026 14:31

KrazyKatty · 18/07/2026 14:28

I think YABU as it sounds like you didn’t make it clear to DSis how you intended to split the payment beforehand and I can see why she assumed you meant a 50/50 split.

I’d be annoyed in her shoes too.

She said to her sister that they should treat their parents. Only a CF would assume a 50/50 split from that if the split is between a family of 3 and a family of 1!

MrsKateColumbo · 18/07/2026 14:32

I have the most kids in my family a
So ALWAYS add extra when splitting/treating GPs so that I am covering my kids.

BringMeHome · 18/07/2026 14:32

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.

Or maybe the sister has managed to upset all her family involving the parents she tried to treat.
All for 35 quid - the sister should have just got over it.

Highways go both ways.

BringMeHome · 18/07/2026 14:34

Angelyogini · 18/07/2026 14:30

And one more thing. OP is great at typing here "treating the parent". How is it both mom and sister got confused in real life?

Sister is a cheeky fucker and gains from the situation. She went to mum and got in her ear about it. It’s really common.

backformoreofthesame · 18/07/2026 14:34

Has the heat addled brains ?

thepariscrimefiles · 18/07/2026 14:34

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.

Fuck that! OP paid for herself and one of her parents' meals. It was her sister that involved their parents by complaining to their mum that OP hadn't split the bill 50/50.

Her sister and BIL are cheeky fuckers. If the bill had been split 50/50, they wouldn't have paid towards their parents' meals at all.

TheIdlerReturns · 18/07/2026 14:35

SleepingStandingUp · 18/07/2026 13:06

Surely you overpaid anyway.

35 for Mom
35 for Dad
35 for BIL
35 for Sis
Yours was free.
So it only came to £140 and you paid £70

There's also OP's nephew. A 12-year-old boy, so probably not drinking either.

KnickerlessFatWoman · 18/07/2026 14:35

KrazyKatty · 18/07/2026 14:28

I think YABU as it sounds like you didn’t make it clear to DSis how you intended to split the payment beforehand and I can see why she assumed you meant a 50/50 split.

I’d be annoyed in her shoes too.

But surely she hasn’t clarified it either?

OP posts:
LiquoriceAllsorts2 · 18/07/2026 14:35

MyCrushWithEyeliner · 18/07/2026 14:30

Maybe she’s pretending to be thick to get out of paying her share

Well it sounds likes the parents and two sisters drank wine and the bil and nephew didn’t

OneLimePombear · 18/07/2026 14:35

I think you and your DS are right TBH, it’s just one of those misunderstandings that happens sometimes.

What was wrong was her involving your DM.

mbonfield · 18/07/2026 14:36

I have learnt through bitter experience and money simply do not gel, avoid at all cost.
The situations we have had a family are that 2 members of our extended family refuse or look the other way when it comes to splitting or paying a food/entertainment bill. imagine when i make it plain before the last meal how it was going to work with the split and they could barely speak to me after the meal was over, they had to pay for their fair share!

ReadingSoManyThreads · 18/07/2026 14:38

YANBU

Your sister is a CF.

Can't believe so many people on this thread think treating their parents means the OP should have ended up paying for some of her sister's family's meals!

Angelyogini · 18/07/2026 14:38

BringMeHome · 18/07/2026 14:32

Or maybe the sister has managed to upset all her family involving the parents she tried to treat.
All for 35 quid - the sister should have just got over it.

Highways go both ways.

So why is mom siding with sis?

ThisTimeWillBeDifferent · 18/07/2026 14:38

KrazyKatty · 18/07/2026 14:28

I think YABU as it sounds like you didn’t make it clear to DSis how you intended to split the payment beforehand and I can see why she assumed you meant a 50/50 split.

I’d be annoyed in her shoes too.

You’d be annoyed at actually paying for one of your parents on top of your own family? You think “treating the parents” means you pay for your own family and your sister pays for herself and both of your parents? How generous a treat from you…

DisforDarkChocolate · 18/07/2026 14:38

If you said you'd split the bill I'd assume you were paying half.

If you said I'll pay mine and one parent, you were fine.

onlygeese · 18/07/2026 14:39

I would have assumed the same as your sister from what was said at the start. But thinking it through I see your logic. I think you just need to be clearer in future.

wfhwfh · 18/07/2026 14:40

I am totally with you, OP. What it boils down to is an adult man (your BIL) expecting a single woman to pay for him and his son. I think that’s distasteful and Im surprised your sister doesnt see that.

My sister and I have different-sized families and when we treat our parents, we just each add an extra meal to our respective bills - it’s easy. The people being treated are your mutual parents. Currently, your sister is treating noone - in fact, you (a single-income household) are subsidising her (a two-income) family.

And for her to involve your mum is mean-spirited and in bad taste.

To the previous poster who said she always goes 50:50 with her sister despite the fact she (the pp) has a smaller family - this is very generous of you. You are the one subsidising and this is a lovely gesture. But if you were the one expecting to be subsidised and asking for it (ie OP’s scenario) it’s mean and bad-mannered.

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

BringMeHome · 18/07/2026 14:42

Angelyogini · 18/07/2026 14:38

So why is mom siding with sis?

In my family it would be because my brother is loud and causes issue, he’s the cheeky fucker and moans the loudest. My mum tries to keep him happy. She sees me as the one that is easier so the pressure is put on me to keep the peace even when he is wrong. It’s really common for this dynamic to be in families.

I don’t stand for it. I tell my mum she needs to go with what is right, not with what he wants but she doesn’t want to challenge him. It’s easier to challenge me because I act like a reasonable person.

Thingsthatgo · 18/07/2026 14:42

If they’re paying 50/50 then OP is the only person treating her parents to a meal. Her SIL and BIL are paying for themselves and their son.

TheIdlerReturns · 18/07/2026 14:42

Seems like a simple communication issue. You said you agreed to pay for one parent and sis would pay for the other, but she seems to have heard 'splitting the bill' which works in her favour. Also, there's just you but your sister has got DH to share costs. Are they wealthier than you? Either way, I would just stand your ground and say the agreement, as far as you were concerned, was to pay for yourself and one parent, which you've already done. Your post is reminding me of The 1% Club quiz show somehow.

TheCurious0range · 18/07/2026 14:43

FWIW DB and I often go halves he has more children than I do, we split things 50/50 it's fine, if we couldn't afford to eat out and were counting every penny I wouldn't eat out tbh.

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