Readers’ forum: Where does tax liability lie?

I act for a large number of personal service companies which have operated on the basis that IR35 does not apply and have paid corporation tax and then extracted post-tax profits by means of a small salary and dividends. I’ve been reading the proposals for PAYE liability for non-compliance Off-payroll working (IR35) – calculation of PAYE liability in cases of non-compliance (tinyurl.com/342mweyz).

If my understanding is correct it suggests that at the moment liability where the end user is large or medium or in the public sector lies with that end user rather than with the personal service company (PSC). So what’s to stop all of my clients who are engaged by such end users from writing to HMRC and saying ‘on reflection I think that my contract was with the off payroll rules – please refund all of the tax I have...