How do I record a duplicate payment as an EFT, when the original check was recorded also, but slow to arrive?

Helping you record a duplicate payment is my priority, steve237.

We can create another check for the duplicate payment and ensure to use it on your future bills for the said vendor. Here's how:

1. Click the + New button in the upper-left corner and select Check.
   
2. Choose a vendor in the Payee field and select the affected Bank Account.
3. Enter the Payment date on when the duplicate payment happened.
4. Go to the Category details section and select Accounts Payable in the CATEGORY column.
5. Add the Amount and the details. You can add a description if necessary.
6. Hit Save and close.

You might want to read through this article: How to enter outstanding balances for customers and vendors. This will provide you tips on how to manage your vendor balances in QuickBooks Online.

I'm always here should you have any follow-up questions or concerns. Wishing you and your business continued success!