I've been self-employed for just over 15 years now. Every quarter I send the IRS 20% of my *gross* earnings. Period. Come tax filing time I am always within $1000 of whatever my total tax liability comes out to be. In my personal opinion (and we call know what those are like) doing the paperwork and projections is just a waste of time and effort. If you just send the IRS 20% of the gross earnings each quarter, then come tax time you'll be fine.
In the 15 plus years I've been doing this, I've always gotten some of it back in the form of a refund. In the two years I actually owed the IRS more, it was less than $500. That's not a big deal either. Just write the check and be done with it. Here's how this works.
If at the time you file your tax return, you owe the IRS lses than $1000 or less than 10% of your total tax liability (whichever is *HIGHER*) then no underpayment penalties will be assessed. So by sending the IRS 20% of your gross business income, when you file your taxes and take into account your allowed business expenses it would be unusual to "not" be within the threshold that would trigger a penalty.
Also note that quarterly taxes are not due on a "true" quarterly basis. For the 2020 tax year the schedule is:
1st Payment January 1 to March 31 July 15, 2020
2nd Payment April 1 to May 31 July 15, 2020
3rd Payment June 1 to August 31 September 15, 2020
4th Payment September 1 to December 31 January 15, 2021
The 1st payment is normally due by April 15th. But it's changed for 2020 due to the C-virus.
