You must pay it as you earn or receive income during the year. There are two ways to pay as you go. If you are an employee, your employer likely withholds income tax from your pay. By revising your W-4, you can increase your withholding to cover the income from your job and from direct selling. If you do not pay tax through withholding, or do not have enough withheld, you may have to pay estimated tax.
Estimated tax is used to pay both income and self-employment taxes.
For more information on estimated tax, see Publication 505 . You do not have to pay estimated tax if you meet either of the following exceptions. You had no tax liability last year, you were a U.S. citizen or resident for the whole year, and your tax year covered all 12 months. Use Form 1040-ES to figure your estimated tax and make quarterly estimated tax payments. If you did not pay enough estimated tax or have enough income tax withheld, you may be subject to a penalty for underpayment of tax.