The IRS urges everyone who works as an employee and has income from other sources to perform a Paycheck Checkup. This includes income from sharing economy activities, interest, dividends, self-employment, capital gains, or prizes and awards. A Paycheck Checkup can help you avoid receiving a lower refund, an unexpected tax bill or underpayment penalty when you file your tax return next year. You can do a checkup using the IRS Tax Withholding Estimator or Publication 505. You can pay taxes throughout the year anytime.