@SuperiorGCAZ  "I received a customer check on 2 invoices & a vendor refund on an overpayment,"

@SashaMC  "My suggestion would be to manually create the deposit in Quickbooks by putting the two payments in undeposited funds then make the deposit with those transactions."

@SuperiorGCAZ"Thanks but QB won't allow me to do that. The vendor refund I entered as a credit, so the from account on the deposit is Account Payable & if I try to change to UF..."

Yes, of course you can't record a deposit to the special Undeposited Funds account using a Vendor, nor can you enter an AP Credit using the Undeposited Funds account. Neither of those things would make any sense and they are disallowed by QuickBooks, which @SashaMC  would have seen had he actually tried it.

So...

- Delete the deposit that contains the customer payment.

- Edit the deposit that contains the vendor refund and add the customer payment using the Payments button at the top of the deposit window.