DEAR AMY: My boyfriend’s dad is a CPA, with decades of experience. A few years ago he offered to do my taxes, due to the sudden complexity because of an inheritance – and I was using cheap software for very basic returns. Since taking over my yearly filing he has consistently made mistakes that have cost me quite a bit of money. He left off a major account distribution one year; this should have been easily caught by him. When I discussed the mistake with him, he never acknowledged it was due to his error, nor did he offer to pay the interest I owed. This year, I decided to start filing my tax…