how can I get a receipt for subscription payment?

You can find your invoices in the portal. In order to do this, first you should click on the avatar icon of your account and then click on Settings. Then you need to go to the Billing tab and scroll down to the Invoices section.

You can check and follow this guide:

https://www.jotform.com/help/329-How-to-Check-Invoices

Let us know if you need any further assistance.