#MidnightCrow
frigid dune
velvet lance
If you have already added the item to the Subscription, then you would retrieve the upcoming invoice for it by providing the Subscription's ID to that function.
If you haven't added the item to Subscription yet, then when retrieving the upcoming Invoice for the Subscription you would include the new item in either subscription_items or invoice_items depending on the type of item that it is.
The response to that request is an Invoice, that you can step through to view the impact.
topaz cobalt
That would calculate the total of all the invoice items on the subscription. I am not seeing where I can see just the new item added.
velvet lance
That is correct. What is it exactly that you're looking to do? Do you want to preview the Invoice that would be created if you charged your Customer for just a single item?
topaz cobalt
yes, keeping the billing cycle of the subscription the same and only charging a prorated amount for a new line item.
velvet lance
Then the way I suggested is the correct way. You cannot omit the current items in the Subscription from that preview, they are part of the upcoming Invoice.