Let us guide you through the process of recording the return and the credit to ensure that they are applied correctly in QuickBooks Online (QBO), BaylightContracting.

We understand how frustrating it can be when something as straightforward as this isn't handled properly by the program. You would expect a seamless process, but instead, you're dealing with double credits or open balances, which can be incredibly time-consuming to resolve. QBO should be able to handle this kind of transaction smoothly. To fix this, we'll need to record the original purchase by following the steps below:

1. Click the +New Plus icon and select Expense or Check, depending on how you originally recorded the purchase.
2. Enter the $3,000 purchase of plumbing materials, select your Checking account, and categorize it appropriately.
3. Then, record the return by clicking the +New Plus icon and select Vendor Credit.
4. Choose the vendor from which you purchased the plumbing materials from.
5. In the Amount field, enter $315.04 (the amount of the return).
6. In the Category details, choose the same expense account that you used for the original purchase to ensure it offsets correctly.

Once done, apply for the vendor credit by following the steps below:

1. Click the +New Plus icon and select Expense or Check.
2. Choose the vendor you are returning the items to.
3. In the Category details section, enter the original expense account and the amount of $315.04 as a negative amount. This step is key to not duplicating the credit.
4. In the Payment Account dropdown, choose your Checking account.
5. In the Amount column, enter $0 as the total amount since you’re balancing out with the return.

Lastly, record the bank deposit by entering the amount of $315.04. Let me guide you on how:

1. Go to the New Plus icon and select Bank Deposit.
2. In the Account dropdown, choose your Checking account.
3. In the Received From column, select the vendor.
4. In the Account column, select the appropriate expense account or Accounts Payable if that's how you'd like to offset it.
5. Enter the amount of $315.04.
6. Press Save and close.

Doing these steps, you won't double count the credit, the accounts will reflect the correct balances and the vendor balance will reflect the credit accurately. To learn more about handling a refund or credit from a vendor, you can check out this article: Enter vendor credits and refunds in QuickBooks Online. 

To run reports for your vendor, please refer to this article for guidance on how to run and customize the report: Customize vendor reports.

Moreover, you can refer to this article about managing the bills and their payments in QBO: Enter and manage bills and bill payments in QuickBooks Online.

We are always available to assist you if you need further help with the vendor refund or any QuickBooks-related concern. Feel free to reply to this thread. You have a good one, BaylightContracting.