Why won't it let me mark a paid invoice as paid even though 4 days ago

We need to receive the payments in order for the invoice to be marked as paid, @ruslss. Let me provide you with the steps.

Before we proceed receiving payments, we need to enable first the payment options.

Here's how:

1. Go to the Settings.
2. Select Account and Settings.
3. Then, click the Payments tab and enable the payment methods you want to offer.

Then, Here's how to record and receive payments:

• Go to the Sales menu and select Invoices.
• Find the invoice for which you received payment and click on it.
• Click on the Receive Payment button at the top.
• In the Receive Payment screen:
  • Select the Invoice # you want to receive.
  • Enter the payment date and amount.
  • If applicable, you can apply any discounts or adjust the amount.
• Click Save and Close to record the payment.

Once you receive payments, you'll need to record them in QuickBooks, visit this article for more information: Record invoice payments in QuickBooks.

For future use, if you want to put payments into the Undeposited Funds account before you combine them into a deposit, you can check this article: Deposit payments into the Undeposited Funds account in QuickBooks Online.

If you need further assistance with managing your sales transaction in QBO, click the reply button. I'm always here to help.