To have had enough of ex pissing about with money! CMS/self employed advice needed

[Mumof3almost4]

Left my ex 5 years ago due to domestic abuse, he was verbally vile. We have 3 children.
Money is his last bit of control. He does pay weekly but never a set time and he alternates the amount depending on whether he decides I'm spending the money on the kids or myself that week.
He is obsessed with my movements, if I go to the gym he accuses me of spending the kids money on the gym membership. If I went for a meal with friends, it's the kids money etc. I have always always worked and earn my own money.
He is an absolute dick. I have had police involved and non mol order put in place previously.

I have got to the point I have applied to CMS for a regular amount to be taken from him. He is self employed but has been sub contracted by the same firm for around 8 years, they provide wages. He then sends his income to an accountant at the end of the tax year and always ends up with a rebate.
He earns a fortune compared to me. His very minimum weeks wage before tax is £580, he often does overtime and can earn over £1000 per week.
My question is how his contribution will be worked out. His accountant will be dodgy. Ex will do what he can to pay bare minimum. How do I make sure his actual earnings are what is used to make the calculation?? I have done the application this morning and there's nowhere to include additional information!
I will do whatever is necessary, I've been nice for far too long, he needs to properly provide for his kids
Advice appreciated!!!

If he has a professional accountant I would assume you have to take the accountant at his professional word/calculations (I assume HMRC will audit where they believe it is required). However I assume if he goes self employed can some money go through as "business" rather than wages ( in which case you may not receive CMS at rates equivalent to if he was payee).

Good luck!
There is much experience on here of rp's trying to get CMS to sort out the self employed. Sadly it is likely he will pay himself a minimum wage and the rest as some kind of dividend - or will switch to this once CMS come sniffing. Its a tried and tested route of avoiding paying- the resulting payment i believe is about £7 a week sadly. You can ask CMS to check his tax returns and post out that his lifestyle is incongruent with his reported earnings but it is a long battle from what I understand.

Annoyingly it seems to be an area that the system is happy to let controlling nrps get away with.

Thanks for the replies.
I thought I'd be in for a battle.
It's a bit odd though, he doesn't have a business he is a manual worker classed as self employed. He works for/is sub contracted to work for the same company continuously.

So it,s more freelance rather then self employed, as he is being employed and therefore is being paid a wage.

Just checked an old document. It states he has self employed status as a freelance operator?

Once you have applied and they have assessed it, you can ask for a “variation of income” form where you put all the extra information.

They do ask if you have any evidence though.I had a copy of the consent order where ex had declared earnings much higher than the figure he gave CMA, and statements from companies house showing the assets in his company.

I’m still waiting to hear back after sending that in though. Whilst receiving £5 a week per child, from a company director who seems to have declared himself as earning far less than minimum wage.

It is so frustrating, and is also about control. Sometimes he pays “more than he needs to” (based on the false low figure) but then reduces it or doesn’t pay at all if my life seems to be going too well But at present I can’t do anything as he has been assessed as only being able to afford the £5 a week...

@Goatscheesewithhoney that is appalling! £5 per week?! What an arsehole, I really hope you get it properly sorted soon.
If it was money that was owed to the government it'd be dealt with swiftly and properly. It makes me so angry that they get away with not paying for their own kids.
Is it straightforward to get the variation form?

If he's a manual worker he'll be a sole trader being paid via CIS (20% deducted from everything at source). He will file a tax return each year for his tax to be calculated and that's when the rebate is triggered due to having paid 20% of his whole pay.

He will struggle to lie about his earnings due to his job / how he's paid.

I have no idea how these guys do it! My DH worked relentlessly in the run up to the birth of our DD so that he could have a bit of time with us and the CSA (admittedly a long time ago) decided to take those 3 months of work and changed his maintenance because they said he had earned too much. He had made enough to pay his ex the amount set £595 plus our bills for at least a month. They doubled it and we got into so much debt. I don’t understand how people get away with hiding money! Or why they would do it.

@NoWordForFluffy yes that's it, thank you for clarifying that for me.
Fingers crossed it might actually work out properly then.