How do I go about recording a check transaction where I'm prepaying a bill in quickbooks online. I can write a check, but it doesn't record the credit with the vendor

Thanks for reaching out to the Community space, wade8.

Let me get the help you need in recording a vendor credit transaction in QuickBooks Online (QBO). 

Recording credit for the vendor depends on how you record the purchase. You can either perform the choices below which applies to you:

• If you enter bills you plan to pay later
• If you enter expenses or write checks

Moreover, a check transaction is used to record expenses that are paid right-away or have already been paid. Thus, there isn't an option to apply a vendor credit to it. To be able to track credits for your vendors, a Bill is needed to associate the credit. Doing so will track the account balance and credits using Accounts Payable. 

If you're unsure about what option you'll need to use when recording a vendor credit, I recommend contacting your accountant. 

For more information in recording credit to your vendor, take a look at this article: Enter a credit from a vendor.

If you have any further questions about this, leave me a message below. I'll be around, anytime! Take care.