Are you asking about the "risk" of an audit, meaning how likely will there be an audit?

It seems unusual that the taxpayer suddenly want to add unreported income to his tax return.  Did you ask WHY it was not originally reported and now WHY he wants to report it?

Will adding this income cause him to owe more tax?  Or will adding this income INCREASE his refund, such as EIC, the Additional Child Tax Credit and/or the Covid sick credit?