I have already filed my 2010 taxes and recd my fed and state refunds. Yesterday I recd a corrected 1099-INT from a credit union, correctly increasing the interest paid to me by $16. (They had neglected to include a bonus dividend, and I missed it too.) This will result in me owing about $2.50 in additional federal tax.

My CPA says he is too busy to file an amended return until after Apr 18, and that if I go that route he charge me more than the additional tax, penalties, interest. He suggests just waiting for IRS to bill me for the underpayment of taxes.

However, I am assuming there is some penalty, that will be significantly more than the unpaid tax and interest on the unpaid tax.

Can I just send in payment voucher with a check for $3 prior to April 15, and no accompanying amended tax form, and let the IRS keep the change?

I cannot see wasting my time filling out forms over less than $3.