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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:
KnickerlessFatWoman · 18/07/2026 12:56

Sorry, I don’t know how I managed to bold it all!

OP posts:
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?

Greenqueen40 · 18/07/2026 12:58

No of course yanbu, you have paid for one parent and yourself. Absolute cheeky fuckery if they expect you to pay half!!!

wow217 · 18/07/2026 13:00

Everytime such a post comes on, the reply is the same: this should have been discussed at the time. I don't know how close you are, but if it was my sister I know that I would've been on the phone to her to explain exactly like you've done here.

CleaningWoes · 18/07/2026 13:01

You have overpaid if anything given that your meal was taken off the bill.

KnickerlessFatWoman · 18/07/2026 13:03

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?

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).

OP posts:
KnickerlessFatWoman · 18/07/2026 13:04

wow217 · 18/07/2026 13:00

Everytime such a post comes on, the reply is the same: this should have been discussed at the time. I don't know how close you are, but if it was my sister I know that I would've been on the phone to her to explain exactly like you've done here.

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

OP posts:
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.

KnickerlessFatWoman · 18/07/2026 13:04

CleaningWoes · 18/07/2026 13:01

You have overpaid if anything given that your meal was taken off the bill.

Well, exactly. That’s why I think it’s pretty rich to expect me to split the entire bill!

OP posts:
BlackCat14 · 18/07/2026 13:05

I think you’re right, but it should have been discussed at the time. To say “split the bill” does suggest an equal split so I can see why they thought you’d pay starlight up half the bill. But you shouldnt be subsidising the three of them, I agree you should just pay for one parent each. But I definitely would’ve made that clear at the time.

lifeturnsonadime · 18/07/2026 13:06

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).

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.

KnickerlessFatWoman · 18/07/2026 13:06

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.

It was only my main that was taken off; I still had my other courses and my share of the wine to pay. I didn’t bother quibbling about that as BIL wasn’t drinking, so if we’d been paying exact shares, his would have been less anyway.

OP posts:
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

Recklessismymiddlename · 18/07/2026 13:07

I’d have thought split the bill £105. I wouldn’t be quibbling for a sister and nephew tbh. But I also wouldn’t have involved my mum if I was your dais.

clarrylove · 18/07/2026 13:08

I'm sure her husband can pay for his own meal and that of his son without expecting you to pay half. What nonsense!

KnickerlessFatWoman · 18/07/2026 13:08

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.

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.

OP posts:
Shinyandnew1 · 18/07/2026 13:09

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

And the nephew

Coconutter24 · 18/07/2026 13:09

Have you spoke to your sister about the reasoning of how you broke the bill down?

backformoreofthesame · 18/07/2026 13:10

Yes each pay their own bill and the share the parents costs evenly between the two halves

you Could also suggest that they pay 2/3rds of the shared part since there are two of them but only if you want to fan the flames of a fire !

Shinyandnew1 · 18/07/2026 13:10

They are assuming you’ll pay half of the total bill, you agreed to split the cost of your parents.

I would speak to your sister and explain.

KnickerlessFatWoman · 18/07/2026 13:11

Coconutter24 · 18/07/2026 13:09

Have you spoke to your sister about the reasoning of how you broke the bill down?

As I say, I’ve only just found out that she’d understood the plan differently to me.

OP posts:
lifeturnsonadime · 18/07/2026 13:12

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.

One time, now our kids are older and some of them have partners, out of a party of 12 we paid for 6 and there were only three of us because the treat for the parents was that the son's would split the bill.

We didn't just pay for both parents we paid for one of bils family,

If we wanted a different arrangement we would not have agreed to split the bill,

I think you should have clarified this in advance.

StormGazing · 18/07/2026 13:12

If you’re treating mum and dad then yes you’re right

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!

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.

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