Delighted to have you here, @Susan28562.

I'd be pleased to furnish you with resources on how the recording of your bank transactions works in QuickBooks Online.

When receiving payments from clients, only cleared payment transactions are posted in your bank's online website. Thus, you'll not be able to download and import it in QuickBooks.

You need not worry, you can still mark your invoice as paid as soon as you received the payments. 

Once the payments are cleared and posted on the bank's website, you can now download and import it in your QuickBooks Online account. 

To avoid getting duplicate records of the payments, you can match the imported payment transaction and the manually recorded payments. Here's how:

1. Once the importing process is complete, go to Banking.
2. Choose the Banking tab.
3. Select the bank where you imported the transactions.
4. Choose the For Review tab.
5. Look for the payment transaction.
6. If the system detects a match between your transactions, you can see Match on the Action or Category columns. 
7. If not, expand the transaction.
8. Select Find Match.
9. Locate the manually added transaction.
10. Click Match. 

That should do it! This will allow you to record your bank transactions accurately.

Keep in touch with me if you have other question about managing downloaded and imported transactions in QuickBooks. I'm always here to help.