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HMRC internal manual

COTAX Manual

Interest: how interest is calculated: negative credit interest

Where credit interest originally calculated and posted requires amendment downwards, negative credit interest is posted on to the record. This can happen in the following situations.

  • Credit interest has been repaid for a CTSA AP and that AP is then superseded. The payments on which the credit interest was calculated on the superseded AP are reallocated to the new AP. Credit interest is therefore no longer due and is cancelled.
  • The ‘quarterly instalment payment’ (QIP) signal is changed from ‘N’ to ‘Y’ on the AP. Credit interest was originally calculated as though the AP was a non-QP case and all the tax was due by the normal due date (Word 49KB). When the ‘QIP’ signal is amended to ‘Y’, credit and debit interest is calculated from the quarterly instalment due dates.
  • Payments on which credit interest was calculated are subsequently reallocated and credit interest is no longer payable on these payments.
  • The AP is adjusted and the tax charge is increased.

Negative credit interest is shown as a ‘minus’ credit interest posting in function VPPD (View Payment and Posting details). Where the original credit interest was either reallocated or repaid then the creation of negative credit interest may leave the AP with a collectible balance in the amount that was reallocated or repaid. This amount does not attract late payment interest.


  • COM80011 for a list of forms relevant to this subject
  • COM80012 for a list of functions to use in particular situations
  • COM80013 for legislation applying to this subject.