June 5, 2019 The best way to do a Paycheck Checkup is to use the Withholding Estimator. However, you may need to use Publication 505. Withholding Estimator The Withholding Estimator helps you check if you need to adjust your withholding. Use the results from the estimator to complete Form W-4 and adjust withholding. If you receive pension income, use the results to complete a Form W-4P, and give it to your payer. You can use the Withholding Estimator to determine if you should pay estimated tax. Publication 505 If you have a more complex situation, you may need to use the instructions in Publication 505. This includes those who owe self-employment tax, the alternative minimum tax, tax on unearned income by dependents or receive non-wage income.