Finding out or determining that something got left out of your return after you filed can get fixed. Tax regulatory bodies will ask a bigger question as to ask what and why the omission occurred.
If the matter at hand pertains to, say only a few dollars of interest, you may consider merely filing an amended return. Regulations go into some great detail over what’s called a qualified amended return, or QAR. In which case, you can file amended returns and pay the additional tax and interest, but the IRS won’t come after you and penalize you.
As an aside, the onus remains on the taxpayer – not the preparer – to take action. The preparer’s obligation extends only to notify the taxpayer.