You can now pre-fill all the fields in your payment pages using url parameters. This includes “invisible” custom fields on your payment pages. This makes it more powerful and seamless to send customers to the Paythen payment page from another system or form, with their info already pre-filled. It also makes it easier to track marketing sources and campaigns by passing these values to invisible fields on your payment pages via url parameters.
Read more about using url parameters here, and custom fields here.