Why do I owe taxes at filing time when taxes come out of every paycheck?

Owing usually means your withholding didn't keep up with your real tax, and a few common causes explain most cases. The biggest culprits: a two-income married couple whose combined income lands in a higher bracket than either W-4 assumed; side income, freelance work, or investment gains with no withholding; a large bonus or RSU vest withheld at only 22%; or a W-4 still set from before a raise or life change. Even claiming too many adjustments on your W-4 can leave you short. The fix is to adjust withholding going forward — add extra dollars on line 4(c) of a new W-4 — and, if you have untaxed income, make estimated payments. Don't just accept owing every year; trace the gap and retune. Run a quick W-2 checkup at wealthserene.com/assessments/w2-tax-checkup.