Can I have an underpayment collected through my tax code?
Yes, but you must either:
send your tax return online by 30 December after the end of the year it relates to
send a paper return by 31 October after the end of the year it relates to
You'll also need to show on your tax return that you want the tax collected through your tax code. The amount must be less than £3,000 and you must have enough PAYE income for the full amount to be collected.
