If you're a freelancer, 1099 contractor, or solopreneur in the US, nobody withholds tax from your income the way an employer would. That means the IRS expects you to pay estimated tax four times a year — and if you underpay by too much, you can owe a penalty on top of the tax itself. Here's the actual method, no app required.
Net income = total money you've received from clients, minus your deductible business expenses (software subscriptions, a portion of home internet, equipment, mileage, contractor fees you paid out, etc). Log every payment as it lands, not when it's invoiced — cash you haven't received yet isn't taxable yet.
Take your projected net income for the full year and run it through the current federal tax brackets for your filing status. This gives you an estimate of federal income tax owed on that income. It's an estimate, not a filing — you're just trying to get close enough to avoid a penalty and avoid a surprise bill.
This is the part employees don't see, because their employer normally pays half of it. As a self-employed person you owe both halves of Social Security and Medicare tax — currently 15.3% on most net self-employment earnings (up to the Social Security wage base for that portion, uncapped for Medicare). This is usually the single biggest number people underestimate.
Add your estimated income tax and self-employment tax together. That's roughly your total tax liability for the year. Divide by four for a rough quarterly payment target — adjust each quarter as your actual income comes in, since freelance income is rarely even across the year.
The method above works, but it only helps if you actually have the cash on hand when the quarterly deadline hits. The freelancers who get blindsided aren't the ones who don't understand the math — they're the ones who didn't set money aside the day the client payment landed. A simple habit: the moment income arrives, immediately calculate roughly what % of it is "not yours" (tax) and move that percentage to a separate savings account.
This is exactly why I built the Freelancer Finance Kit — a plain spreadsheet (no app, no subscription) that logs income per client, tracks deductible expenses by category, and runs this same estimate automatically as you log payments through the year, plus a dashboard and an invoice template.
Get the Kit — one-time $19This is a general educational overview, not personalized tax advice. Tax brackets, self-employment tax rates and thresholds, and rules on what counts as a deductible expense change and vary by situation — always confirm your specific numbers with a licensed accountant or the IRS's current guidance before you pay.
Also: What a freelance invoice actually needs (free template) →