First year doing gig work - how much should I pay in Q4 estimated taxes?

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Illustrative scenario prepared by my practice.
For informational purposes only. Not legal advice.
Hypothetical question

This is my first full year doing Uber and DoorDash. Made about $42,000 total (after gas and expenses, net is probably $30K).

I haven't paid ANY quarterly taxes because I didn't know I was supposed to. Q4 payment is due January 15. How much should I pay to avoid penalties?

Also - do I calculate based on gross ($42K) or net after expenses ($30K)?

Illustrative response

$7,000?! I don't have that saved up. What happens if I can only pay like $3,000 now?

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Illustrative response

Don't panic, but act now. Here's your situation:

What you owe (rough estimate on $48K):

Action items: (1) Make a large estimated payment NOW via IRS Direct Pay (irs.gov) to stop the penalty clock, (2) set up quarterly payments going forward (Q1: Apr 15, Q2: Jun 15, Q3: Sep 15, Q4: Jan 15), (3) open a separate savings account and set aside 25-30% of every payment.