To record that refund that you've received for your rental, you'll need to create a vendor credit and deposit the money that you've received. Once done, you can connect the deposit to the vendor credit. This process will record the exact happening on your transactions into QuickBooks Online.
Let's start with generating a vendor credit. This makes sure the credit hits the expense account you use for this vendor.
To do that:
Click on + New at the left pane.
Select on Vendor credit.
In the Vendor drop-down, select your vendor.
Depending on how you record the rent with this vendor, enter the Category details or Item details. Usually, this is the category, product, or service you’re getting a credit for.
Hit on Save and close.
Once done, proceed with depositing the money that you got from the refund.
Hit on the + New button.
Choose Bank Deposit.
In the Account drop-down menu, select the account where you got the refund.
From the Add funds to this deposit section, select the vendor who gave you the refund in the Received from section.
On the Account field, select Accounts Payable. Know that you need to pick Accounts Payable so you can tie the refund to the vendor credit.
Enter the method your vendor used to refund you in the Payment method field.
Key in the amount that you received in the Amount section.
Press on Save and close.
After that, we'll have to link the credit to the deposit to keep your vendor expenses accurate. Please follow the step number 3 on the link below to accomplish this: Enter a refund from a vendor.
You can also visit these articles about applying credits and tracking your expenses in QuickBooks Online for reference: