Greetings, @DSGardenSupplies.
When you're busy managing a business, the last thing you should have to deal with is the inability to apply payments to customers account. Let me help you sort this out.
To ensure your merchant sales are recorded as income and applied to your customers account, it's account should be "Accounts Receivables".
On the other hand, undeposited funds is an account created by QuickBooks Desktop which holds your funds until you decide to deposit it (record) to a specific bank account entered in the system. You also have the option to set this as your default Deposit to account for all of your account receivables.
You can always manually update the accounts where your transactions are recorded. Just open the said payment and change the Deposit To.
For additional insights, you may check out these articles:
Please feel free to let me know if you have other questions about depositing your income transactions, the Community always has your back. Wishing you well.