I sent a payment link, customer paid. "System-recorded deposit for QuickBooks Payments" , Deposit is to undeposited funds. bank has the deposit. How to pay an invoice?

You'll need to link the deposit on the invoices and match it to the transaction from the bank, ken133. Let me outline the details below.

All online payment transactions are credited to Undeposited Funds, which acts as a default account that retains funds until they are transferred to your bank account. To apply the deposit entry as an invoice payment, follow the steps below:

1. Select + New, then Receive payment.
2. Choose a name from the Customer ▼ dropdown to see all unpaid and outstanding credits.
3. In the Payment date field, enter the day you received the payment.
4. In the Outstanding Transactions section, choose the invoice to mark as paid.
5. In the Credits section, pick the deposit.
6. Click Save and close.

After that, let's go over these measures to create a Bank deposit and select the Bank account where the actual payment was deposited:

1. Go to the New (+) button.
2. Select Bank Deposit, then choose the Bank Account where the payment was deposited. 
3. Enter the date when the actual deposit was made.
4. In the Select the payments included in this deposit section, mark invoice payment that's paid.
5. Review the payment details, and ensure they match the downloaded bank transactions.
6. Click the Save and Close button.

Once done, navigate to the Transactions menu and select Bank transactions to match the deposit with the downloaded entry in the For review tab to prevent double income. I'm adding a screenshot below for reference:

Moreover, refer to this guide to familiarize categories and other actions: Categorize online bank transactions in QuickBooks Online.

Furthermore, reconciling an account in QuickBooks Online is always a good procedure to ensure your accounts are balanced and accurate.

Lastly, do you need help tracking your sales and ensuring they're on the correct account? You can do it with the guidance of an accountant. Speak now with a QuickBooks Live Expert for more personalized assistance.

You can count on me if you have follow-up questions about invoice payments or the reconciliation process. I'll be here to provide the resources and information. Have a great day!