If you don't want to reveal your non-job income, i.e., from dividends or interest, you can calculate the additional tax amount that should be withheld from your paycheck and report in Step 4c. To calculate the additional tax amount for this income, you may use the Tax Withholding Estimator or divide your non-job income by the number of pay dates in the year. Please note that if this is the only job in your household, you can check the box in Step 2c. Also, the extra withholding will be based on the income amount.