Underpayment Tax Situation

dori2o

HMRC are correctly using the figures provided to them by your former employer.

That is all they can do. That is all the current legislation allows them to do under PAYE.

If you contest that the figures they have provided to HMRC are incorrect then you need to approach the employer as Unholyangel says and ask they submit corrected details or pay you what you are owed.

Do this in writing and ensure that in your letter you ask them to confirm where they made payment to should they insist that repayments were made to you in the months after you left.

If you still contest and can prove no payments were received then write to HMRC claiming employer error (stating you believe the employer is responsible for the error) and include the bank statements of the account the employer claims they made payment to (assuming you didn't receive the payments).