One of the more obscure filing deadlines for Self Assessment purposes relates to a claim to have your tax underpaid for a year recovered by an adjustment, an increase, in the PAYE stopped from your salary in a future tax year.
For underpayments year to 5 April 2015, the filing deadline is fast approaching, 30 December 2015.
You will not be able to request this type of settlement if:
you don’t have enough PAYE income for HMRC to collect it
you’d pay more than 50% of your PAYE income in tax
you’d end up paying more than twice as much tax as you normally do
Underpayments that are agreed to be settled in this way for 2014-15 will be adjusted in your code number for 2016-17.