To use multiple forms of payment to pay a single invoice :

When posting payments in Impromed, add multiple Payment Names of Scratch Payment with the corresponding amount for each card
Click the Post Payment button
Open the Scratch Pay desktop app by clicking the notification on the bottom right of your screen.
Click on the line item of the invoice for which you would like to process a payment.
On the right side of the screen, click on Terminal/Manual payment.
The screen will display the full amount of the invoice under the label Enter Charge Amount. Click Change below the amount.
On the popup screen, enter in the amount you would like to charge to the first payment method and click Confirm.
This amount will now be displayed on the screen and you can now take a payment for this amount via the terminal card swipe or manual input options.
The side bar will then update with the remaining amount on the invoice to make a second payment.
You may edit this amount again if you are splitting the invoice into more than two payments. The bottom of the right pane will display a transaction log of all payments made for this invoice.

Impromed / Scratch Checkout Integration User Guide

Processing payments directly from Impromed using the Scratch Checkout desktop app