An app pays you. Nobody withholds. Here is what follows.

What the app handles, and what it leaves with you

If you carry on a trade or business as a sole proprietor or an independent contractor, the IRS treats you as self-employed. Driving, delivering, or selling through an app often fits that description, though your own agreement with each platform is what settles it.

For self-employed income, no one withholds Social Security, Medicare, or income tax along the way. The IRS describes estimated tax as the method self-employed people use to pay those taxes during the year, because there is no employer doing it for them.

Platforms may send you a Form 1099-K or a Form 1099-NEC after the year ends. Those forms report what you were paid. They do not change what you owe, and the IRS is clear that gig income has to be reported even when no form arrives.

The two thresholds that decide it

The first is $400. If your net earnings from self-employment for the year are $400 or more, you have to file a return and you generally owe self-employment tax on them. Net earnings means what the work brought in minus the business expenses that went into it, such as the costs of the car miles or the materials for the things you sell.

The second is $1,000. The IRS says individuals, including sole proprietors, generally have to make estimated tax payments if they expect to owe $1,000 or more when their return is filed. That figure counts all of your tax for the year, not only the part from gig work, after withholding and credits are taken into account.

Put together: a few hundred dollars of side income in a year may only mean a line on the return. Steady income from one or more apps is where the $1,000 mark tends to come into view, because self-employment tax alone is 15.3% of 92.35% of net earnings, before any income tax.

When there is a W-2 job too

Plenty of people drive or sell on the side of a salaried job. Tax withheld from that paycheck counts toward the year, so it can cover some or all of what the side income adds. The IRS notes that people with wages can avoid estimated payments by asking their employer to withhold more, using the extra-withholding line on Form W-4.

Which route suits you depends on how much the side work brings in and how evenly it arrives. Some people prefer one steady adjustment at the day job. Others would rather pay each quarter so the side income carries its own tax.

Finding where you stand this year

A workable first pass takes three numbers: what each app has paid you so far, the business costs you can document against that, and a rough sense of the rest of the year. From there, the self-employment part is arithmetic, and the income tax part is a range that depends on your bracket, deductions, and other income.

If the total you expect to owe after withholding reaches $1,000, the four estimated payment dates start to matter. They fall on April 15, June 15, September 15, and January 15, each moving to the next business day when it lands on a weekend or holiday. The due dates guide covers them, and the penalty for coming up short, in more detail.

The quickest check is to try your own figure in the set-aside calculator. It shows the self-employment tax, a federal income tax range, and what that works out to per week and per quarter.