Side hustle and a W-2 job: raise withholding or pay quarterly?

If you have a regular job and earn extra on the side, your employer’s withholding doesn’t cover the side income. You have two ways to deal with that.

Option 1: Raise your W-2 withholding

Submit a new Form W-4 to your employer and enter an extra amount to withhold each paycheck (Step 4(c)).

Good for: steady, predictable side income.

• Automatic, nothing to remember.
• Withholding counts as paid evenly through the year, even if you start in October. That makes it a good fix if you’ve missed quarterly payments.
• Downside: less flexible if your side income swings a lot.

Option 2: Pay quarterly estimated tax

Make payments with Form 1040-ES by each due date.

Good for: side income that varies or is growing fast.

• You adjust each payment to what you actually earned.
• Downside: you have to remember four deadlines.

How much extra to cover

Side income usually gets taxed at your top bracket, because your salary already fills the lower ones. Add 15.3% self-employment tax on 92.35% of the profit, and the total is often higher than people expect.

Example (single, $60,000 salary, $10,000 of side profit): about $2,400 of extra federal tax, or 24% of the side profit, even after the 20% QBI deduction.

The set-aside calculator gives your exact figure. Enter your W-2 wages, and it counts only the extra tax from the side income.

Can you mix both?

Yes. Many people raise withholding to cover a baseline and make an estimated payment if they have a big month.