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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:
Rhaidimiddim · 18/07/2026 15:37

KnickerlessFatWoman · 18/07/2026 13:03

Where do you get that I thought my parents were paying for themselves? I said, the plan was to treat our parents.

The bill was £35pp. I paid £70 - my share and one parent’s. The rest of the bill was my sister’s share and one parent’s (another £70) and then my BIL and nephew’s shares (the final £70).

So they expected you to subsidise them, as well as paying for your parent! So they are being CFs.

Ewock · 18/07/2026 15:38

You are right op. You and your sister said you'd treat your parents. Therefore you each pay for a parent. No reason at all why you should subsidise your sis family for their meal

BunnyLake · 18/07/2026 15:39

Rhaidimiddim · 18/07/2026 15:37

So they expected you to subsidise them, as well as paying for your parent! So they are being CFs.

Yes. It’s amazing how many people on here don’t get it. I guess they all must have enough money to not be concerned about the maths.

burnoutbabe · 18/07/2026 15:39

TheCurious0range · 18/07/2026 15:30

That's if you see the food itself as the treat, rather than the occasion and time spent together

Indeed. If I was the bil or nephew I may not see a dinner out with my parents in law as a particular treat! Just supporting their spouse by attending.
m(it may be a lovely place to eat or just mums favourite and they aren’t fussed on the menu)

PrincessScarlett · 18/07/2026 15:40

BunnyLake · 18/07/2026 15:36

That’s thoughtless of the sister then. Logic should have told her it was three against one.

Yes it is thoughtless of the sister. However, this thread shows though that sister isn't the only one with her view as many people have said in the same situation they would have split the bill 50/50 and equally many others wouldn't.

Clear communication by all parties is key.

OneFineDay22 · 18/07/2026 15:40

As a Pp pointed out, your parents are usually paying for her whole family to eat free, where you’re only one person. How much free food have they had? Why are they expecting you to pay for both parents while they only pay for themselves?

YANBU

Ponoka7 · 18/07/2026 15:41

I agree with the way you've done it. I can't help feeling that she's involved your Mum because if you don't give in, your parents will feel bad and pay what your Sister wants.

TheOnlyLivingBoyInNewCross · 18/07/2026 15:41

TheCurious0range · 18/07/2026 15:09

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.

Edited

🤦🏻‍♀️

How, just how, are the two situations the same?

Imagine you and your sibling go shopping for a painting for your parents. You choose a lovely one which costs £500. You’re happy because you can afford your share of that - £250. Then your sister pops another painting in the basket because it’ll look lovely in the den which her DH and her DS game in. It also costs £500. When you get to the till and are presented with the bill for £1000 she cheerfully pays her half - £500. Are you REALLY claiming, without even blushing, that you’d happily stump up the remaining £500 without quibbling even though it means you have paid for the WHOLE of your parents’ present which you were going to go shares on?

No wonder online scammers thrive 😂

BeSassyOpalSquid · 18/07/2026 15:43

You both agreed to treat the parents. That means you both pay equal share for the parents.

You didn’t agree to treat her family! Pretty obvious and I don’t understand why it needed any clarity.

Both agreeing to treat THE PARENTS means sharing that cost, and that’s all.

You have already subsidised the sister by paying for your meal even though you didn’t get to enjoy it and it was refunded.

Out of order for her to discuss it with mum.

SweetnsourNZ · 18/07/2026 15:45

KnickerlessFatWoman · 18/07/2026 13:08

But if you do that, where is the “treat” from the other side? My sister agreed we’d treat our parents - if we split the bill 50/50, she isn’t contributing anything.

I think your sister and you are at cross purposes about the actual treat part, and that is the problem. You are thinking about the treat being an actual plate of dinner, so fair enough, one plate each to pay for. Your sister on the other hand is thinking of the family meal as a whole being the treat for your parents, so whole bill 50/50.
No perspective is wrong as we have done both in our family, but you just weren't on the same page unfortunately.

PrincessScarlett · 18/07/2026 15:45

Ponoka7 · 18/07/2026 15:41

I agree with the way you've done it. I can't help feeling that she's involved your Mum because if you don't give in, your parents will feel bad and pay what your Sister wants.

Oh interesting point. Yes parents will feel guilty and pay the difference to the sister.

I bet this is the last time dad will let anyone else pay. So sad that it's soured what should have been a nice treat for parents.

PeachySmile2 · 18/07/2026 15:47

Your sister is deluded and needs to apologise to you. Why would you pay for one of their meals? You pay for your meal and half your parents. They pay for their meals and half your parents

Calliopespa · 18/07/2026 15:47

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 sort of agree with this OP.

"Splitting" sounds like your Dsis takes half and you take half.

I can also see why you would think it fair that you each just pay for your nuclear family (ie; just you, in your case) and one parent each, BUT I do think that is the less natural interpretation of "splitting," and I would have worded that differently had that been what I had in mind - something like " we each shout a parent."

However, in the circumstances, I think you are both BU, because after your meal came off the difference is circa £30 and for that amount it would have been better not to make the whole event a bit of an unfortunate saga. In your Dsis' circumstance I'd have just shut up about it, and in yours would probably just have said "I'm sorry I misunderstood" and quickly paid the difference. Sometimes money just isn't worth unpleasantness - and you did get your meal free.

Justyouwaitandseeagain · 18/07/2026 15:48

KnickerlessFatWoman · 18/07/2026 13:08

But if you do that, where is the “treat” from the other side? My sister agreed we’d treat our parents - if we split the bill 50/50, she isn’t contributing anything.

I suppose if your parents usually pay the whole bill then usually everyone else pay nothing. They are suggesting you collectively treat your parents by splitting the bill in half on this occasion - so they pay half of what your parents would usually pay, and you pay half. it's clearly a shock to them for you to expect them to pay more.

if instead you'd previously al split the bill equally, so your parents pay for themselves, you pay for yourself and your sisters family paid for themselves, then the rationale to each cover half the parents share would make sense.

not saying they were right, but I can see how they are justifying their viewpoint.

Calliopespa · 18/07/2026 15:49

PrincessScarlett · 18/07/2026 15:45

Oh interesting point. Yes parents will feel guilty and pay the difference to the sister.

I bet this is the last time dad will let anyone else pay. So sad that it's soured what should have been a nice treat for parents.

So sad that it's soured what should have been a nice treat for parents.

This.

I'd have just sucked it up, even had it not been what I expected. £30 is budgetable.

BeSassyOpalSquid · 18/07/2026 15:49

If your sister has misunderstood what should be obvious and is FAIR, that’s entirely on her OP. Frankly I think she is being very cheeky!

GertrudePerkinsPaperyThing · 18/07/2026 15:50

You are 100% right OP. Your sister and her husband are CFs!

If her way was the plan, it should have just been you and your sister taking the parents out. Her way works out as you either paying for one of her husband or son, or paying for both parents whilst they just tag along for the ride.

No wonder she liked the plan if it was the way she understood it!

You were generous to pay the £70 because your meal was taken off bill, so arguable the bill should have been in five shares, with you only paying one. edit - sorry have just seen about it only being your main taken off, and that BIL wasn’t drinking (as wasn’t the 12 yo of course). Although soft drinks often cost as much as wine, and 12 yos often go for a pudding etc

LemonyCurd · 18/07/2026 15:51

Whilst the ‘logic’ of 50/50 could make sense (if you ignored reality), the fact of the matter is that single person sister is paying the entirety for the parents in this situation and CF sister is getting a free pass again. Nope. This is insane. Anyone with any sense of fairness (or sanity!) can see this.

KermitTheToad · 18/07/2026 15:51

OP is your sister my sister?😀 My Dsis had form for this when our kids were preteens. Me my dd , my DM, DSis and 2 D nephews would often to out to lunch, and we would split the bill evenly to treat our mum. Except her 2 boys were big eaters and would order from adult menu, ( say £18 each) while my dd would usually have a smaller meal or her and I would choose from the 2 for £20 menu. So DSis and I would pay £46 each, whereas technically I would actually be paying for one of my nephews . My bill plus half DM should come to £29, and sister's should come to £63.

Bellyblueboy · 18/07/2026 15:51

This sort of thing often happens with single people - the single person tax!

In this case six people went out to dinner. Splitting the bill evenly means OP treats her parents to a meal and her sister just pays for herself, her husband and her child.

Sister and BIL are clearly very cheap!

ChiefCookandBottlewasher7 · 18/07/2026 15:53

Can you imagine what atmosphere you and your stupid sister created for your parents with this idiotic squabbling? Irrespective of who is right and who is wrong, why spoil the vibe? It is like giving a gift and then crapping all over it. Your parents will be more concerned about your relationship with your sister in the future, as in when they die - surely they hope you will be supporting each other, not quibbling over thirty quid, when the parents are no longer with you?

Ilovelifeverymuch · 18/07/2026 15:54

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.

By that logic then OP has paid for both parents and part of sisters meal as well so what has sister contributed to treat their parents?

There were 6 people at £35 each to totalling £210.

If they split is £105 each then sis has just paid for herself her husband and her kid while OP has paid for both parents.

Given the idea was to treat their parents not split the bill equally how has sis treated her parents?

And if sis has an issue or thought there was a misunderstanding she should have reached out to OP not go to their mother.

They agreed to treat their parents not split the bill and frankly sis is ridiculous to expect splitting bills equally when she has a husband and child while OP is single.

BeSassyOpalSquid · 18/07/2026 15:54

In addition, OP paid, it was the sister who queried and raised it with the parent.

Sister is at fault. Sister is the one who could have called OP, and could have sucked it up without querying and causing discomfort.

Twinkletoesandspaghettios · 18/07/2026 15:57

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

Read the OP. She said “the bill came to £210”

JumpingRabbit · 18/07/2026 15:57

Originally I was thinking you had a partner too, in which case I’d have just spilt the bill, cba not just splitting over one extra child but when I realised it was only you, I think you did the right thing.

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