This part of GOV.UK is being rebuilt – find out what beta means

HMRC internal manual

National Insurance Manual

Class 1: Treating as paid: Negligence established: Opinion is not disputed

If no response is received, or the response does not dispute the opinion, the unpaid NICs cannot be recorded on the NI account.

In some cases, the unpaid Class 1 NICs may already be recorded as paid. If so, any NICs that are erroneously shown as paid must be removed from the NI account. NIM12119 provides further information on removing NICs from the NI account.