I have a full time job where I get a W-2. In addition I occasionally freelance on the side as a contractor and receive a 1099-MISC.
The freelance work is very irregular and hard to predict. It's possible that I'll do zero freelancing one quarter and then some amount of freelancing the next. I am sure to do a reasonable amount of freelancing work this year, but the net revenue I receive could vary by as much as 2-4x.
Last year I did not file any estimated taxes (it was my first year freelancing). Turbotax was kind enough to provide an estimate (presumably based on similar/identical income for 2015) for estimated taxes and the quarterly schedule for when I need to pay said taxes.
My understanding is that late payments are subject to penalties. This year, to date, I have had almost zero freelancing income (maybe ~$400), but I expect that this quarter I will have substantial freelancing income.
Additionally I did not pay any estimated taxes by April 15th (I didn't make nearly the amount of money freelancing required to pay the estimated taxes that turbotax suggested).
What's the best strategy for someone in my position?
Can I simply pay estimated taxes on the money that I earn (or will earn) in a given quarter (e.g. estimate the tax liability on the money I earned that quarter and pay just that so some quarters I might pay zero and other quarters I might pay a few thousand dollars)?
Am I subject to a late penalty because I didn't pay estimated taxes in April even though by income by April was negligible? How do people handle highly bursty/irregular freelancing income?