In my iOS application, I need to accept payments from the user. I am using UPI for the same. I have followed the following document provided by UPI
http://www.npci.org.i
Have not tried it but it was mentioned in the document about a url parameter on clicking of which we should show the transaction details to the user.
This should be a URL when clicked provides customer with further transaction details like complete bill details, bill copy, order copy, ticket details, etc. This can also be used to deliver digital goods such as mp3 files etc. after payment.
We could send a url with a url scheme that redirects to the app or an universal link that our app can handle.
Again I have not tried this so I do not know if this works as I think it should or whether it would exactly solve your issue.
https://www.npci.org.in/sites/all/themes/npcl/images/PDF/UPI_Linking_Specs_ver_1.5.1.pdf
You can use the url parameter to pass your website url with the get method with order id or payment id as parameter. Once the payment is successful, it is mandate the UPI provider to hit the URL. The purpose of the URL should be keep updating the transaction status and trigger then end user an email or SMS with the transaction status.