you must estimate your total tax for the year.
you can base your estimate on prior year's tax , or 90% of this year's tax, whichever is smaller.
each quarter your estimated tax paid and withheld must be at least 25% of the estimate, even if your income is uneven,
if your estimate is based on this year's tax and turns out to be wrong you may be penalized.
you can compensate by overestimating.
The operative factor is 25%.
@crash345u
