I do not want grief.
So I keep every receipt for the year, report everything, and leave it to the accountant to deal with. I do not like paying taxes, but it's a nessesary evil, and I do not have time to deal with bullshit. So I just write my check, complain about it, and do not worry about it in the next quarter.
For those who do not know.. if you are self employed, show a profit, you must report taxes quarterly in the states.
