DP may be affected by this, but I don't expect him to owe a lot of money, if any, but it could be some.
He occasionally does agency work in the construction industry - machine driver. Sometimes he was paid under the Construction Industry Scheme, sometimes he was paid by an umbrella company.
He didn't have any choice in this, if you wanted to work, you had to go by their rules. I suspect that the agencies and the umbrella companies were all connected and I think similar things went on in supply teaching and probably NHS bank staff. It worked like this:
The agency would place him on a site and he was supposed to be paid say £14 an hour to drive the machine, but they required him to sign up to a specific umbrella company. They also told him to submit an expenses claim for mileage and lunch each day, even though the jobs were generally local.
When he was paid, they would pay him NMW for the hours he worked, add on his expenses, an allowance for holiday pay and a random bonus and pay an amount that was more than what he would earn on NMW but less than if he was paid the £14 an hour that he was supposed to be, and supply a pay slip that was made up of NMW, expenses, a random bonus and made no sense at all (I generally understand these things and gave up trying - I helped DP do his tax return for his mix of employed/self employed and umbrella work and I basically crossed my fingers when I pressed submit).
The umbrella company would obviously make quite a bit out of it, but less tax would be paid by DP had he been on a straight PAYE £14 an hour job, but as I said above, if he wanted to work, he had to follow the system and he was also losing out here, even though on paper he might have paid less tax than he was suppposed to.
The construction unions were trying to fight the system and this explains the problem.
He hasn't done much of this sort of work over the last couple of years and when he has, it's been on the Construction Industry Scheme, which treats him as self employed for tax purposes, takes some tax off and it all comes out in the wash when he does his tax return.
As well as being a huge tax scam, the aim of the exercise has been to take away job security from people working in the construction industry, basically a huge amount of builders and other workers on construction sites are on this system and they go from job to job and while they should always be able to get work, they have no job security and it's the agencies that make all the money because the construction companies don't employ people directly.