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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:
WaltzingWaters · 19/07/2026 07:12

No you’re completely correct and your DSis is being a complete CF. As you say, had you split the entire bill then you’d have been paying for your parents meals entirely and dsis only covering her family. And you paid extra anyway if your meal had been taken off.

Wadsworthy · 19/07/2026 07:13

KnickerlessFatWoman · 18/07/2026 14:23

If it’s petty, why can’t my sister just pay her share? If none of it matters, why am I the petty one and she’s not?

I agree, @KnickerlessFatWoman but often single people get stiffed in this way. A lot of married people not good at maths on this thread ...

Just explain to your sister that when you said "split" you meant split your parents' meal bill ie each of you pay £35.

Recklessismymiddlename · 19/07/2026 07:14

But I also think the Dsis shouldn’t have gone running to the mum to complain. If id been her I’d have picked up the phone to the op myself and not complained to my mum and said there had been a misunderstanding and sorted out that way.

Wadsworthy · 19/07/2026 07:18

the single tax that so many coupled people on here seem to blindly apply to these situations without thinking.

100% @OneAquaFatball ! Very well put, and I must remember that phrase, "the single tax."

Nursemumma92 · 19/07/2026 07:18

Wow how a thread changes. Some of your responses to people are absolutely deranged.

Splitting the bill over 2 cards implies it is a 50:50 split. Do I think you should have to pay the full £105, no. But judging by the way you have responded to people on here I can see why your sister is upset and why she would assume you were doing 50:50.

CrazyMidget · 19/07/2026 07:19

OneSparklyGoat · 19/07/2026 03:03

I do this whenever possible, too but some places will not allow it.

We only seem to go out with old friends where we all know our routine. We split evenly (by person). If anyone has significantly more, they’ll always take it off the top before the split. One friend likes craft cocktails and will do this.

It helps that we are horrified by the idea of not contributing fairly and that a couple of us enjoy doing the math.

If we are in a nicer place one of us will take the bill and the others send their share later.

Edited

Oh, that's interesting that some places won't allow it. I've only done it once so far, so I haven't had much experience. The article was saying that it's a whole lot easier to start with separate tabs than split it up at the end. I can see that if you're a big group, they might not want to start ten different tabs. Although, having said that, they'd have to do that for ten different customers who didn't know each other, wouldn't they.

CrazyMidget · 19/07/2026 07:20

Wadsworthy · 19/07/2026 07:18

the single tax that so many coupled people on here seem to blindly apply to these situations without thinking.

100% @OneAquaFatball ! Very well put, and I must remember that phrase, "the single tax."

Exactly. It's not fair.

Cattywillow · 19/07/2026 07:24

There are 5 in my family, 3 in my brother’s family. We took my parents out for lunch and split the bill for our parents. So we divided the total by 10 and he paid 4x that and I paid 6x that. It would never occur to me to do it any differently. Why would I ever expect my sibling to subsidise my family?

Treebaubles · 19/07/2026 07:24

Op I’m not sure why you are getting such a kicking here. I can’t see what’s so hard to grasp. You are totally in the right to pay for yours and half your parents. Your sis is being cheeky.

PhaedraTwo · 19/07/2026 07:34

Wadsworthy · 19/07/2026 07:06

YANBU, but you'll probably need to explain it. Married people get very bad at maths - they can get mistaken in thinking that 2 people = one person, when it comes to bill splitting.

You and your sister have very different ideas about splitting the bill. Neither of you is mathematically wrong; but I think your sister is a bit cheeky to expect you to pay half of the total bill, when it was just you, in contrast to the 3 people in her family. (and your main course was rubbish/inedible from the sounds of it).

But this is typical behaviour pf married/family people. They just don't think, and obviously you sister sees her family (3 people) as one unit, and you (1 person) as one unit.

You need to explain your maths to her, and the concept of fairness!

That's so true.

Justbreathagain · 19/07/2026 07:47

Totally agree with you OP. You agreed to treat your parents not pay 50 % of the bill. Your sister should not be expecting you to pay towards her, her husband's and sons food! Unless you agreed to that of course. I would not consider them taking your main off the bill as that was a discount in general for the food not being great. You ds is a CF
Edited to add I actually can't believe her cheek. She wanted 1 person to pay 50 precent of of the bill to treat the parents. Is she hard up or something ? And also why tell her parents and not you

dontmalbeconme · 19/07/2026 07:51

In my mind, you parents generally pay the whole bill. You agree to "treat" them, so you split the whole bill that they would have otherwise paid equally. So I'd have expected 50:50.

Jennalong · 19/07/2026 07:56

As long as you've paid for everything your family ate , plus half of what your parents had . I can't see the problem that everyone is having in here .

Mycatsasuperstar · 19/07/2026 07:59

I think this is just another example of single person tax, who end up having to pay more and / or subsidising couples and families. Not sure of its the case here but often families or couples see themselves as a unit so expect to be treated as one cost and thars super unfair. OP you are definitely not in the wrong here

MsPrufrockk · 19/07/2026 08:05

I'm confused why OP is getting told she should have paid half and 'treated' her BIL and nephew as well as her parents? Definitely the single person tax coming into play here!

I've had it before when I've gone out for dinner with 2 couples and at the end of the night they wanted to split the bill 3 ways, and none of the 4 other people understood why I laughed and said erm no? I assume all the people saying @KnickerlessFatWoman should have paid half agree with those couples?

StormInaDcup99 · 19/07/2026 08:09

I definitely agree that OPs sister is in wrong and is" hard of understanding".

However OP does come across as rather difficult /angry/rude in some posts, but I'm not sure if that is reflective of her in real life, or simply because some posters are so dismissive of the situation she has been put in by CF/entitled/money grabbing Sister

PretendToBeToastWithMe · 19/07/2026 08:12

I think the way you’ve broken it down (£35/head) when it wasn’t a fixed price is problematic if you haven’t discussed with this your sister before because in her head that might not have been an accurate way to estimate each person’s share and then the £70 seems a bit random.

In my mind depending on how many drinks were ordered it wouldn’t be fair to just split the bill by the number of people attending the meal because drinks are so expensive. The fact your main got taken off would be irrelevant to me personally as it would have been unexpected but others may disagree. It’s so subjective what each person would think is a fair way to do it so I can see why there was confusion and they may not even understand how you came to £70.

I do think your sister was being VU mentioning the cost and confusion to your mum who was meant to be treated for her birthday! That’s the most unreasonable part of this whole story. The last person she should have mentioned it to was the person being treated to a birthday meal as it makes it awkward and ruins the treat.

StormInaDcup99 · 19/07/2026 08:15

dontmalbeconme · 19/07/2026 07:51

In my mind, you parents generally pay the whole bill. You agree to "treat" them, so you split the whole bill that they would have otherwise paid equally. So I'd have expected 50:50.

@dontmalbeconme but that makes no sense

Eg let's say OP income is 50k a year
Let's say sisters and husband is 100k a year

Op is paying 100pc of all her own utility costs insurance taxis mortgage house maintenance etc

Why should she effectively have to subsidise food for sister BIL and nephew when she is always financially worse off already?

Thr sister is totally out of order

KnickerlessFatWoman · 19/07/2026 08:22

Birdsongsinging · 19/07/2026 04:51

The whole point of going out for the meal was to treat the parents. Why should the husband and child pay equally? They are innocent bystanders!

If you and your sister go halves you have both spent exactly the same. Simple.

“Innocent bystanders”? There hasn’t been a murder! They ate food that has to be paid for!

My sister and I shouldn’t have spent exactly the same; that’s the point.

OP posts:
Cannotbelievepeoplecanbesojudgemental · 19/07/2026 08:22

Realistically, if you had simply taken your parents out as the 3 of you, it would have cost you the same as your sister is asking for. Therefore, her contribution would be zero as she only paid for her family. I'm in agreement with you. That's not her 'treating' anyone.
I'd also be very upset about your sister speaking to parents about it. That's going to negate any 'treat' they'd received. Have you spoken to her yet?

Wheesht2 · 19/07/2026 08:23

Exactly the same happened to me, my mum and dad bil, sis, sil and brother, I was on mounjaro only had a starter at £8,00 but brother asked for my card thought we were splitting it 3 ways but he insisted that he and I split it because our big sister and bil do so much running around for our parents as she lives close to them, £103.00 pounds my £8.00 starter cost me, I was annoyed at the time but luckily I can afford it. I don’t think you are in the wrong though.

Birdsongsinging · 19/07/2026 08:23

KnickerlessFatWoman · 19/07/2026 08:22

“Innocent bystanders”? There hasn’t been a murder! They ate food that has to be paid for!

My sister and I shouldn’t have spent exactly the same; that’s the point.

I disagree, you have both spent the same amount on your parents treat meal!

Ally886 · 19/07/2026 08:24

This reply has been deleted

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BunnyLake · 19/07/2026 08:24

ReadingSoManyThreads · 19/07/2026 01:54

What I realised is that it's lucky you never put it all on your card, as sister would only have transferred over 50% to you, instead of the correct amount i.e. her meal, BIL & nephew + one parent's meal.

I can see from this thread, and your sister's appalling actions in telling your mum, spoiling the treat, that she has form for being an entitled madam.

Glad you are standing up for yourself against all the people who think your cheeky fucker sister is in the right. She's bloody not.

So many people not reading your comments properly too which is annoying, OP never said they were splitting the bill, she said they would both treat their parents, so logically, that means each sister will pay for one parent. Why the fuck are people thinking OP should have paid for some of her sister's/BIL/nephew's meal?!

Also, in terms of "splitting a bill", why does everyone on here assume that means a 50/50 split? A bill can be split with people paying for what they've had. Surely "split down the middle", or "split in half", should be the terms used for people expecting a 50/50 split, rather than split proportionally to who had what.

Edited

There are a lot of dim people on here. Anyone with any self respect would not be demanding the single person pays the same as the couple with a twelve year old.

user1492757084 · 19/07/2026 08:25

I'd have paid 50/50.
Split the bill usually means equally.
The treat was that your parents had a meal with all of their family, including children.

Similar if you had invited your parent's sister and or a child of your far-away brother. If you used the term split the bill and agreed then you signed up for paying half.

You siblings both sound mean spirited. Fancy telling your mother how much the gift of the meal was!! It's terrible that you quibble over small, one off, treats to your parents.

Next time your parents will want to pay for themselves. Your father's generosity has not rubbed off on you. You risk the bond with a sister for 35 pound!

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