If you’re self-employed or own a business that doesn’t withhold taxes from your income, the IRS expects you to pay estimated taxes four times a year instead of once in April. The due dates are April 15, June 15, September 15, and January 15 of the following year. Miss those dates and you’ll owe an underpayment penalty on top of whatever you already owe.

The easiest way to make the payment is through IRS Direct Pay at irs.gov/directpay. You enter your bank account info, select “estimated tax” as the payment type, choose the correct tax year, and submit. It’s free, there’s no account to create, and you get a confirmation number immediately. The other option is EFTPS (Electronic Federal Tax Payment System), which requires enrollment ahead of time but lets you schedule payments in advance. You can also mail a check with Form 1040-ES, but that’s slower and gives you no instant confirmation.

Don’t forget California. The state has its own quarterly estimated tax payments with the same due dates. You can pay through the Franchise Tax Board website at ftb.ca.gov. Most trades business owners in the LA area owe both federal and state, so budget for both when you’re setting money aside.

Figuring out how much to pay is where most people get stuck. The simplest safe harbor rule is to pay 100% of last year’s total tax liability divided into four equal payments. If your adjusted gross income was over $150,000 last year, that threshold goes up to 110%. As long as you hit that number, the IRS won’t charge an underpayment penalty even if you end up owing more when you file.

If your income is growing significantly from last year, you might want to estimate based on the current year instead. The target is paying at least 90% of what you’ll actually owe. For contractors and trades businesses where income can swing from quarter to quarter, this takes more guesswork. A rough approach is to take your year-to-date profit each quarter, project it forward, calculate the tax, and subtract what you’ve already paid. It doesn’t have to be perfect, just close enough to avoid penalties.

A good habit is setting aside 25 to 30 percent of every payment you receive into a separate savings account. That covers federal income tax, self-employment tax (which is 15.3% alone), and state tax. When the quarterly due date comes around, the money is already there. The business owners who get into trouble are the ones who spend everything and then scramble to find $8,000 or $15,000 four times a year.

Solid bookkeeping for trades businesses makes quarterly payments far less stressful because you can actually see your profit in real time instead of guessing. When your books are current, calculating your estimated payment takes minutes instead of being a shot in the dark.

If you’re behind on estimated payments or have never made them, start now. The penalty accumulates daily on the underpaid amount, so a late payment is still better than no payment. And if your income situation is complex or changing, working with someone on tax strategy can help you figure out the right amount to pay each quarter so you’re not overpaying and tying up cash or underpaying and getting hit with penalties.