How do I enter a customer payment by credit card towards one of my vendor invoices

I'll help with your question about paying bills in QBO, MH-PFL.

There's no option to directly use a customer's payment to close an invoice. You'll need to create a bill payment transaction to pay the bill. Here's how: 

1. Open the bill that you want to pay. 
2. Click Mark as paid in the upper-right hand corner.
3. Make sure all details are correct.
4. Enter more details in the Memo section if you want to indicate that this payment is made using the customer's payment.
5. Click Save and close.

Here's an article for more details: Enter Bills and Record Bill Payments in QuickBooks Online.

You'll also want to use the Billable Expense feature. It will let you invoice the customer for all the bills and expenses incurred on behalf of them. Here's an article for more details: Enter Billable Expenses.

Feel free to check out these articles for additional guidance and reference:

• What is the Difference Between Bills, Checks, and Expenses?
• Print a Customer or Vendor Register

Please know that you can always reply or reach out to us again if you have other questions. We'll make sure that everything is sorted out. 

Do I do it the same way for a partial payment of the invoice?  I have being using Vendor Credit for the partial payments to get the account balance to match.  Is this method okay also?

We have two ways to record your partial payment using vendor credit, MH-PFL.  

For the first option, we can do this in the Pay Bills section. I'll show you how.

1. Go to the + New button.
2. Select Pay bills.
3. From the Payment account drop-down, select the account you paid the bill from.
4. Enter the Payment date.
5. Select the checkbox for the bill you made a payment towards.
6. Enter the amount to be applied to the bill. You can use the Credit Applied column to enter any credits.
7. Click Save and close.

You can also do this by opening the bill, click Mark as Paid. From there, you can select the specific vendor credit you'd like to apply for the partial payment.

For more details, you can check out this article: Enter a Credit from a Vendor.

Also, I'd recommend pulling up the Bills and Applied Payments report. This way, you can verify that the payments you've recorded are applied to the bills accordingly. Just go to the What you owe section from the Reports menu's Standard tab.

Please don't hesitate to let me know if you have other concerns about managing vendor transactions in QuickBooks. I'm just around to help. Take care always.