1. Find the deposit. Go to Bookkeeping > Chart of Accounts, open your bank account register, and locate the deposit. You can also search for it from + New > Bank Deposit by date and amount.
2. Open it. Click the deposit line to expand it, then click anywhere on the row to open the full deposit screen.
3. Check what's included first. A single deposit is often several payments batched together, customer payments, a refund, a cash sale. Deleting removes all of them at once, not just one line, so confirm that's actually what you want.
4. Select More, then Delete. At the bottom of the deposit screen, click More, then Delete. Confirm when QuickBooks asks.
5. Check Undeposited Funds. Every payment that was part of that deposit lands back there. If you only meant to fix one line, this is where it gets messy, you'll need to rebuild the deposit from scratch instead of just removing the mistake.