On further digging in a fourth chasing call it appears my client received a taxable expense payment in 2012 which seemingly has been included in his code for each following tax year even though no subsequent P11Ds have been submitted by his employer. I'm not aware how HMRC systems work, but surely somebody should update an individual's code number based on the latest available P11D submission? . This failure appears to have been going on for nearly a decade and despite specifically questioning the coding restriction in my January 2021 letter the 2019/20 calculation once again included it.
Fair play to HMRC as yesterday I received a p800 calculation for 2019/20 which included overpayments for all indate prior tax years from 2017/18 onwards. My attention turned to all the tax years from 2012 that are out of date where my new client overpaid small amounts of tax seemingly because of HMRC system failures. I found the following which may be of use. I'll write a letter unless anyone can see a flaw in this idea:
If you think you have overpaid tax in tax years that are ‘closed’ to claims, there is a rule known as Extra-statutory Concession B41 which can allow HMRC to repay tax for those earlier years.
This concession only applies in situations where HMRC or another government department, such as the Department for Work and Pensions, have made an error in your tax affairs and where there is no doubt about the facts of the case.
The relevant part of the concession reads as follows:
‘...repayments of tax will be made in respect of claims made outside the statutory time limit where an over-payment of tax has arisen because of an error by HMRC or another Government Department, and where there is no dispute or doubt as to the facts...'
In our experience, it is rare for HMRC to grant this concession so you will need to set out clear evidence, as to what the error was which resulted in you paying too much tax.
We have produced an example letter that you can use to write to HMRC regarding a B41 repayment.