I have sent invoices that were sent and paid, but they were not paid through QuickBooks. How do I link the invoices with the identical payments received?

I understand the importance of properly recording your transactions, sophiamassad. 

If you haven't recorded any Receive Payment transactions to the paid Invoices, we can either automatically or manually match the payment deposit from your bank account to the Invoices. QuickBooks can only automatically detect matches according to the following conditions; 

• If they have the same date.  
• If they have the same amount. 
• If they have the nearest similar payment date.

However, here's how to manually match the payments with the Invoices:

1. Go to Transactions, select Bank Transactions
2. Select the correct bank account.
3. Under the for review tab, find the payment.
4. Click the payment and then select match.
5. Filter by Invoices.
6. And then select Match.

For future reference, visit this article if you want QuickBooks to automatically process your customer payments and categorize them into the correct accounts: Record invoice payments in QuickBooks Online.

If you have more queries on recording payments or any other QuickBooks-related matters, we're always available to assist. Stay safe.