"If you expect to owe more than $1,000 in federal income taxes that are not prepaid through withholding, you have to make quarterly estimated tax payments. "
Does this rule mean I have to make quarterly estimated IT payments of 1/4 of the entire amount I expect to owe, or just enough to get down to owing under $1,000 the following April? It seems to be the former, but I treat it as the latter (and have never been questioned by the IRA about it). For example, if I expect to owe $1,800, I have paid about $600 in the third quarter, $600 more in the 4th quarter, and $600 more in the following April. Most of my income occurs after June 1st, the start of the third "quarter" for estimated tax purposes. I have no way to have taxes withheld because none of my income is from W-2 or an IRA's RMD, both of which have withholding provisions.
In an somewhat related question, could the federal subsidy from the ACA be used as a backhanded withholding method? I have no advanced premium payment via the subsidy, so I anticipate a subsidy (tax credit) of about $900 coming my way. Could I use that $900 as partial payment of my federal income taxes which would drop my total taxes due to under $1,000. I haven't found anything on point about this (i.e. the "safe harbor" rule and estimated IT payments), but I'm going to do it anyway.