You will need to open a discovery enquiry if
A discrepancy discovery enquiry will be appropriate where there
is a single issue to be addressed (the revision of the income tax
liability) and the enquiry window for the year is closed
and there are no penalties. In all other cases the
discovery enquiry will need to be worked in the Claimant Compliance
Centre (CCC).
See
CCM13200 for guidance on opening a
discovery enquiry.