Overview

Create a new invoice for a customer. Invoices can be created manually for one-time charges or custom billing scenarios outside of the normal subscription cycle.

Example: Create a manual invoice for a customer who requested additional services not covered by their subscription.

Conditional Requirements

Condition	Required Fields
Always	`customer_id` OR `customer_old_provider_id` (at least one)
Always	`currency`
No `line_items` provided	`total`
`line_items` provided	`line_items..unit_price`, `line_items..quantity`
`line_items.*.tax_name` is set	`line_items.*.tax_rate`
`line_items.*.tax_rate` is set	`line_items.*.tax_name`
Both `customer_id` AND `customer_old_provider_id` are set	Must reference the same customer
Both `subscription_id` AND `subscription_old_provider_id` are set	Must reference the same subscription