Some taxpayers may need to make estimated tax payments 

https://www.irs.gov/newsroom/some-tax

https://accountinginstruction.info

Some taxpayers earn income not subject to withholding. For small business owners and self-employed people this can mean making quarterly estimated tax payments.  Anyone in this situation should check their withholding using the Tax Withholding Estimator on IRS.gov. If the estimator suggests a change, the taxpayer can submit a new Form W-4 to their employer.