Discovery Decisions: Earliest date at which Discovery Decision should be made
CCM13050 lists the occasions on which a person’s income tax liability is revised. Where the revision results from the Revenue correcting the taxpayer’s return, (CCM13050 2nd bullet), the statute specifically directs that you should wait 30 days (in case the taxpayer rejects the correction) before making your discovery decision.
In all other circumstances, you can make your discovery decision immediately after the income tax liability has been revised. It does not matter that the taxpayer will in some (though not all) of the circumstances listed have the right of appeal against the revision. Where the taxpayer appeals, the determination or settlement of the appeal counts as another revision of the income tax liability. If you have already made a discovery decision because the income tax liability has been revised, you can make a further discovery decision if the income tax liability is revised again when the appeal is determined or settled.
See CCM13200 for guidance on making a discovery decision.