If you're self-employed, April 15 isn't just tax day — it's also the deadline for your Q1 estimated tax payment for the current year. Miss it, underpay it, and the IRS quietly tacks on an underpayment penalty that compounds quarter over quarter.
The good news: there's a clean rule that, when followed, turns this from a guessing game into a math problem with one right answer.
The 110% safe-harbor rule, in 60 seconds
If your adjusted gross income last year was over $150K, the IRS asks you to prepay either 90% of this year's tax, or 110% of last year's tax — whichever is smaller. Hit either number across all four quarterly payments and you owe no penalty, even if you owe a giant balance in April.
Most clients pick the 110%-of-last-year route. It's simpler. You already know last year's number.
Safe-harbor is a floor, not a ceiling. Paying it doesn't mean you've paid enough — it means you won't be penalized for paying too little.
How we calculate Q1 for a creator with $400K revenue
- Last year's federal tax: $112,400
- Safe-harbor target: $112,400 × 110% = $123,640
- Divided by 4 quarters: $30,910 per quarter
- Q1 payment due April 15: $30,910
That's the floor. If you're expecting a bigger year, pay a touch more. If you had a brand deal cancel and revenue is down, talk to your CPA — there's a workaround called the annualized-income method that can lower your Q1 if income is genuinely lower.
Why the IRS' "penalty" probably isn't worth dodging
The current underpayment rate is 8%. That sounds bad until you remember it's an annualized rate applied quarter by quarter. Underpay by $10,000 for a single quarter, and the penalty is roughly $200. Sometimes the right move is to hold cash and pay the small penalty — especially if your alternative is liquidating an investment or maxing a credit card.
We help clients think through both options each year. Want us to look at yours?