Yeah, TurboTax is currently saying I owe $15 underpayment penalty for a $5,500 underpayment so it doesn't really bother me. At the same time I have a $1,500 CA refund which confuses me a bit - why is one way over and the other way under? Now, our income was a bit mixed last year - wife switched jobs and we moved house mid-year, plus she had a third job for a few months where I think she was taxed at a low level.

And income for this quarter (Jan-Mar 2015) is going to be low for me, possibly even negative, as I've spent a load on a new website and travel, and I won't see the results for at least a few months from now. So I can adjust my estimated income to "low" but then re-adjust it again later to more accurately reflect the income later? In fact, could I do it a month or two before each of the four estimated payments?

Question. Why would a person make these estimated tax payments if they're only a few hundred $ over or under each year tax refund / owing wise? Just seems pointless to me.

Is it a way for the Treasury to amass more money to use throughout the year?

Rene, I was under the impression that if one underpaid or didn't pay once, the penalty was indeed slight, but that if one did the same in the next year, the penalties became larger -- that one couldn't get away with not paying appropriate estimates year after year.