Click on the name of the restaurant to open the restaurant menu (in the top left corner).
Click on "Subscription".
Click on "Change plan".
This will open a screen with the billing information.
Go to "Invoice history" (bottom of the page).
Click on the date to open the download page.
Click on "Download invoice" or "Download receipt".
NOTE: Invoices are downloaded in PDF format to the assigned folder on your device (usually the "downloads" folder).