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HMRC internal manual

Compliance Handbook

Penalties for Failure to Notify: How to process a penalty: Supplementary penalties

Where we have assessed a penalty but the potential lost revenue (PLR) has been underestimated, we may assess a supplementary penalty based on the additional PLR. This allows you to increase the original penalty.


  1. We assessed a penalty in the wrong amount due to a transcription error when the assessment was made. The wrong figure is discovered after three weeks. We can make a further assessment of the omitted PLR and the related penalty if we are still within the time limit for making the original penalty assessment.
  2. We assessed a penalty on Frank based on an estimate of the amount of potential lost revenue. Later, we find that Frank’s tax liability was underestimated. If we are still within time to assess the additional tax due from Frank, we can also make a supplementary penalty assessment within 12 months of the end of the appeal period for the assessment for the additional tax.

The time limits for issuing a supplementary penalty assessment are as set out in CH74200 but run from the date of the further assessment to recover the further PLR or the date the additional PLR is ascertained.

FA08/SCH41/PARA16 (6)