Quote from DisciplinedHedg:
Again, from form 2210, unless I'm misunderstanding things, you don't need to guesstimate your profits.
All that is required for estimated taxes is that you pay the smaller of the tax amounts of the current tax year OR previous year. ie. if you make $80,000 in 2002, but end up making $100,000 in 2003...the smaller is $80,000, the quarterly is $20,000. As long as you make quarterly payments of $20,000, even if you make $100,000 the following year, as far as the IRS is concerned you've paid your estimated taxes in full.
So if you have any doubts of what you will make next year, just pay what you're paying this year in quarterly payments for next year, and you'll be covered regardless of your taxes next year. If you owe more, you can pay at that time; if you paid too much, you can get it back.
If I'm wrong about this, I apologize. But, I believe this information is dated. Now, I believe, if your income exceeds last years' your estimated payments must be within 10% of the actual due. AND if your profits are 4th quarter loaded, you'll pay a penalty for not having made bigger estimates earlier... This from my CPA from '98 and '98 when I had monster 4th quarter gains and big increases over previous years... (not only from my CPA, I paid the penalties)
There was a transition period, that if you made more than the prior year, the "safe haven" was to make an estimate greater than you paid last year. I received a schedule form the IRS about this... it started about 105% of last years and increased over a few years to as much as 112%. Now, I think, it's "within 10% of actual due".