# Small-Business Tax Calculator 2026
Self-employed workers and small-business owners face a straightforward but easy-to-bungle tax reality: estimate what you owe, then pay it in quarterly installments before the IRS penalizes you.
NerdWallet's Small-Business Tax Calculator helps owners project their 2026 income and self-employment tax liability. The tool works by accepting basic income figures and automatically computing both regular income tax and the self-employment tax, which covers Social Security and Medicare contributions. Self-employed individuals pay both the employer and employee portions, totaling about 15.3 percent on net earnings above $400.
Here's the critical part: the IRS expects quarterly estimated tax payments from business owners who won't have taxes withheld from paychecks. Quarterly deadlines fall on April 15, June 15, September 15, and January 15. Miss these and you face penalties and interest charges that compound quickly.
The calculator removes guesswork from the initial estimate, but accuracy matters. Overestimate and you'll get a refund later. Underestimate and penalties kick in. Most filers should aim to pay 90 percent of what they owe this year, or 100 percent of last year's liability, whichever is smaller.
For business owners with variable income, quarterly estimates can shift throughout the year. A strong first quarter might require larger payments, while a slow fall could lower your obligations. The calculator lets you adjust projections as actual earnings emerge.
Record-keeping remains your responsibility. Track income, expenses, and quarterly payments in detail. The calculator gives you a number, but supporting documentation protects you if the IRS audits your returns.
Small-business owners often overlook estimated taxes until a painful bill arrives. Using this tool early and setting calendar reminders for payment dates keeps you ahead