How do I create a supplier payment on account? Payment for a pro-forma invoice?

Hello there, @adezyanian. I want to ensure you'll be able to create a payment for your supplier in QuickBooks Online (QBO).

Thanks for sharing information about your concern. To help you with this, you can simply use the Pay bills feature to create a payment for your supplier. I'll guide you on how:

1. In your QBO account, select the +New button and choose Pay bills.
2. Check the box of the bill you need to pay. 
3. Enter the amount in the Payment field.
4. When done, select Save & close. 

For reference, check out this article: Enter and manage bills and bill payments in QuickBooks Online.

Also, with QBO its easy to bill a customer for an expense. To do so, simply select the Billable checkbox and enter their name in the Customer field. For the detailed guide, read this link: Enter billable expenses.

I'll be always here ready to lend a hand if you have any other concerns about paying your supplier in QBO. Have a great day ahead and stay safe. 

Create a dummy supplier invoice for 0.01p - make an expense for your payment on account and allocate the payment to the 0.01p with the remainder being a credit on the account  - go back and delete the dummy invoice. POA should now be there