You can keep track of payments directly in your Parent Portal by viewing your billing history and downloading previous invoices.
To access your billing history, log into your Parent Portal and navigate to the "Manage programs" section. Select the enrolment you'd like to view billing information for, and you'll see a "View" button in the "Billing Information" section.
Clicking the "View" button will display a popup showing your billing history, along with the option to "Download" the invoice for each payment.