Why Is My Tax Estimate Different Than I Expected?

A few things commonly explain this:

• Flux pools all your income sources together. If you have more than one job, your combined income may push you into a different tax bracket than any single source would suggest on its own.
• 1099 income includes self-employment tax. If part of your income is 1099, a 15.3% self-employment tax is factored in on top of regular income tax — this can meaningfully raise the estimate compared to W-2-only income.
• The estimate is based on your year-to-date pace. Early in the year, a small amount of income gets annualized (projected out to a full year) to produce an estimate, so the number can shift as you log more throughout the year and the projection gets more accurate.
• Your tax profile matters. Filing status, state, and dependents all affect the estimate — double check these are set correctly in your tax profile.

This is always an estimate meant to help you plan, not a substitute for filing your actual return.