The number that made quarterly taxes stop being scary was simple: set aside 25 to 30 percent of every single payment the moment it arrives, into a separate savings account you don’t touch for anything else. It’s not exact, but it’s close enough to avoid the panic of owing a huge lump sum in April.
I also started tracking deductible expenses in the same spreadsheet as income, logged the same day rather than reconstructed later from memory, which turned tax season from a week of digging through receipts into about twenty minutes of copying numbers.
The habit that mattered most wasn’t a clever tax strategy, it was just moving the money out of sight the same day it arrived.