This could suggest that you failed to report some item of income that was reported to the IRS by the payer. Check the Tax Return Transcript for other lines where the "PER COMPUTER" line (calculated by the IRS from information returns filed by payers) differs from the similar line above it (without "PER COMPUTER", from items you reported on your tax return). Check your Wage & Income transcript for items of income that you did not report or reported differently from what was reported on the information return provided by the payer. For example, check to see if you reported a different taxable amount on pension income than the pension plan reported as taxable.
The discrepancy is likely too large to be explained by a tax underpayment penalty.
