Its a Child Maintenance one

I would contact cms. These men are a disgrace.
Do not give him any breakdown. He's not entitled to it

This!

Or at least this unless there's a good reason to do something different.

There are 2 ways of dealing with this,
To say, ah your last act of vengeance I see, using DD as a pawn no less. Well you haven't met half of her costs...ever! So how about you leave it and do as you want to. Pay 0.

Then he has nothing to try and hold over her, no control.

Or

She can write an exhaustive list, and have the satisfaction of him knowing what needs are met for DD.

Bit in honesty he's likely to not do anything.

It's shit and it's not right. I'm sorry

I wouldn't be saying 25% of anything. Why should he pay 25% of the rent or electric when it's a house he doesn't live in? If the rent is £500 it's £500 whether she's there or not. If the utilities are £200, but would be £160 if she wasn't there, then the fair thing would be to ask for 50% of the difference. So 50% of £40. You couldn't just say £200 utilities, I'll pay £100 plus £50 and you pay £50. That means he's contributing to YOUR life as well as his daughters.

Give a total figure without a breakdown. Just say this covers all her educational materials, travel costs, sanitary products, hair cuts, clothes, food etc. Point out that it has always been far in excess of any contribution he has made through CMS and does not account for loss of earnings by being the primary carer for a child with SEN.

If she really must go down the financial break down route, could she start by sending a list without costs?

accommodation
electric
gas
water
council tax
clothes
toiletries
cleaning products
sanitary products
etc etc

Make it a really long, detailed list (to emphasise just how many costs there are) without itemising prices (because he will quibble over them anyway).

A normal 18 year old I wouldn't assign a clothes budget but if she's disabled...

🤯 "normal"

I know it won't have been posted with the intention of offending, but disabled people are normal too.

I agree with previous posters and wouldn't advise supplying BUT realistically if your sister is going to get zero anyway, she may as well try.
Your sister should pay her own half of bills, dad responsible for 50% of dn so

25% of mortgage/rent
25% water
25% food etc

Does your niece get dla or pip or whatever it is at 18 to support access in community? If there's more to be paid above that, then more of that

A normal 18 year old I wouldn't assign a clothes budget but if she's disabled to the extent she wouldn't ever be able to shop independently or work then 25% of that too

Does she need anything specialist above and beyond? Certain shampoos etc? How does she get to college? Petrol? Bus pass?

I'd list everything can think of and if he starts picking it apart then just quietly live life without his pathetic contributions. He shouldn't get away with not providing but he likely will.

I'd personally put:

Food
Travel
Mobile
Clothing
Appointment expenses
Days out
Pocket money

I wouldn't start putting bills and rent he will just pick it apart. Plus does having an 18 year old in the house cost much more than not having an 18 year old in the house? I have 2 teens and without them here I'd still be paying all my bills. I'm sure they'd go down a little but probably not too noticeable. This is how he will look at it. Because he's a deadbeat.

Thing is no matter what she decides to include he can decide doesn’t matter when you’re just doing a private arrangement.

You could put in water/gas:electric and rent and he will go but you’d pay that anyway so no.

You could include hair cuts and he could decide he knows somewhere cheaper so would only chip in a fiver.

Get her to list everything if that’s what she wants, but do so knowing he won’t agree. So when he then goes no only this much she can “agree” he feels he won and she gets something 🤷🏻‍♀️

I think you just want people to agree with you. He shouldn't get away with anything, but how are you going to make him pay for the next 12 months? You're not really are you? Deadbeats like him get to get away with it.

Yes but still an adult.

Im childless i didnt want drama in my life.

I can sympathise with this situation.
Trying to argue with an idiot is impossible and a complete waste of time and energy.

I’d respond once. Get her to look at her bank statements and list all the costs on there. Rent/mortgage, utilities etc.

I'd definitely make an application with the CMS. Whatever you tell him he will argue about so let them deal with his arseholery.

My ex listed beauty treatments at £20 per month….when DD was 4 years old. That’s the level of lunatic I have to deal with!

Who is still in full time education

Weird how people say this about the Mum, but never the deadbeat dad who's trying to avoid paying the minimum legal obligation he has towards his child.

Oh do one. Do you have a disabled dependent? The father should be paying to support.

I have been down this road. It's shit. My own view is whatever breakdown she gives, he will want a breakdown of breakdowns or "receipts as proof" and then he will find a reason why they're not proof. She is not going to win this one. I'd report him immediately to HMRC and if she has the "I'll take cash in hand" message, I'd give them that too. I'd go through CMS, just for sheer amount of hassle it'll give him. They will go by last year's calculations anyway so if he's submitted a tax return then tough. I fucking hated men 🤬

The child is now an adult.
Its all about money on mumsnett.

Ok, there's what should happen via CMS and then there's dealing with the situation you have. If your sis wants to go that route then I would include
Food
A portion of the utilities
Travel to college
Travel to medical appointments
Additional costs for ND related equipment or treatment
Phone bill
Any other tech costs eg laptop
Clothes
Toiletries
Any hobby costs
Allowance

I mean there’s two options isn’t there.

Give him the details
Don’t give him the details - go via cms

Sounds like either way however she won’t be getting the money.

Its a shit system than not resident parent abuse.