There might be a small penalty if you don't pay quarterly but it is not that much. As long as the tax guy gets his money he is not going to come after our little amount and if you pay the penalty, he doesn't really care. I usually do twice a year when I don't have an employee position and in 20 years have never been questioned, have had to pay sometimes $50 in penalities but just did it. I also know of at least 10 friends who are painters, contractors, beauticians, etc. and they don't do quarterlies either -- just pay at the end of the year. But it is up to you to have the money at the end of the year. That is where it comes in to play and that is why I usually send in June and December so that I don't have a big whallop at April 15th. It would be no different than if you were an employee and did not have enough withheld -- then you pay by the 15th and sometimes have a penalty but you pay -- IRS is happy.