Few, if any, of us will ever have the good fortune about to befall Floyd “Money” Mayweather—a $100-plus million payday for about an hour’s worth of work. But all too many entrepreneurs, business owners and “working folks” regularly face the other side of the Mayweather coin—failing to pay taxes promptly and owing onerous sums to the IRS.

Sometimes it’s because of ignoring the “marriage penalty” that requires married couples to pay taxes higher than the individual spouses would pay individually. The IRS has worksheets attached to Form W-4, Employee’s Withholding Allowance Certificate, to calculate additional withholding, but many taxpayers may be either unaware of the worksheets or find them confusing. Gotcha.