Taxes Are Done - Get Ready for Next Year! Check your W-4. If you got a substantial refund this year (or, worse, had a substantial bill), adjust the allowances on your W-4. Despite what many people think, the number you write down in box 5 on your W-2 has almost nothing to do with the number of people in your family. This W-4 Withholding Calculator makes it easy to estimate your paycheck withholdings.