: When paying the 1st and 2nd quarters of estimated tax payments (Form 1040-ES) due on July 15, 2020, should I make 1 or 2 payments on irs.gov/payments? I read on https://www.irs.gov/businesses/small-businesses-self-employed/estimated-taxes:

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TLDR: As you probably know what your earnings/taxes are for the two tax quarters, I would apply two quarters worth of taxes to the earliest period. Nothing wrong with one for each quarter. As long as the IRS gets the payments they are due, that is what matters.
My rational is that any excess estimated payment become equivalent to rolling over any excess payment from the prior year and is added to your tax id's credit with the IRS, and used up by the taxes on income each quarter going forward.
The goal is to end the year without penalty (from your link):

Generally, most taxpayers will avoid this penalty if they owe less than ,000 in tax after subtracting their withholdings and credits, or if they paid at least 90% of the tax for the current year, or 100% of the tax shown on the return for the prior year, whichever is smaller.

When income is variable in order to reduce penalty at the end of tax year, for individuals Form 2210 is used to declare when such income is received, so applying tax payments earlier for later uneven income allows for a reduction/removal of penalty, at the cost of paying earlier.
From when I did this filling out as an individual taxpayer, I think I underpaid one year due to some reason, and as I didn't pay estimated evenly over the tax year, so I needed to fill out Form 2210 to reduce the penalty by declaring when the income arrived.