Is there a way to create and access Wix Invoices & Quotes directly from your site using Wix Code?
Hello Quentin I am building a complete custom payment checkout flow with automatic invoice generation using the Pay and Billing API. I am happy to say I got the system to successfully create the invoices with all the correct data. However, I have a BIG problem at the very end of the chain: When trying to use the createInvoicePreviewUrl( ) or sendInvoice( ) I get an error.
The interesting part is : When I login with admin credentials it works like a charm. Are those 2 functions’s behaviour intended to work this way?? this makes it imposible to send customers the created invoices, which make the whole idea of an API pointless. Can you please confirm the same behaviour? It’s driving me crazy 
cheers!
Sorry, I can’t help you I don’t know what permission are required to use those API.
I suggest you create a new post to deal with this issue (you can link this one as reference). You can also contact support with that question directly