When you run a business, nobody withholds taxes from your income the way an employer would from a paycheck. Instead, you pay income taxes yourself throughout the year in four installments. The IRS calls these estimated taxes.

The due dates are April 15, June 15, September 15, and January 15 of the following year. These apply to both federal and Idaho state taxes. If a due date falls on a weekend or holiday, the deadline moves to the next business day.

You can calculate payments using one of two safe harbor methods. The first is paying 100% of what you owed last year, divided into four equal installments. If your adjusted gross income exceeded $150,000, that threshold increases to 110% of the prior year. This method protects you from underpayment penalties no matter what you actually owe for the current year.

The second method is paying 90% of what you expect to owe this year. This works if your income dropped compared to last year, but it requires accurate projections. Underestimate and you face penalties.

Most small business owners use the prior-year method because it’s simpler. Look at last year’s tax return, find your total tax liability, divide by four, and send those payments each quarter. No guessing required.

The penalty for underpayment runs about 7-8% interest on whatever you should have paid, calculated from when it was due until you pay it. Miss multiple quarters and the interest compounds. It’s not devastating, but it’s money you could have kept.

Cash flow makes this harder than it sounds. Many businesses have uneven income throughout the year, but the IRS still expects roughly equal quarterly payments. Some owners set aside a percentage of every deposit specifically for estimated taxes. Others make larger payments during strong months to get ahead. As long as you meet the annual safe harbor amount, the timing of individual payments has some flexibility.

Pass-through entities like S corporations, partnerships, and LLCs don’t pay taxes at the business level. The tax obligation flows to the owners, who pay estimated taxes personally. Business tax preparation for these entities focuses on getting the owner’s quarterly payments right, not the company’s.

If you’re in your first year of business and had no tax liability last year, you’re generally exempt from estimated tax requirements. But that first tax bill can be a shock if you haven’t set money aside all year.

The businesses that handle estimated taxes well treat them like any other recurring expense. Budget for them, set the money aside before you spend it on something else, and pay on time. Small business tax preparation that includes year-round support helps you calculate quarterly amounts, adjust when income changes significantly, and avoid the scramble that comes from waiting until due dates to figure out what you owe.

Getting the calculation right from the start is easier than paying penalties later. If you’re unsure whether you need to pay or how much to send, ask before the April deadline rather than guessing and hoping for the best.