# Invoices

An invoice represents the business transaction between a sub-merchant and a customer. In Resolve, an invoice must be tied to both a customer and a sub-merchant. An advance can be taken on the invoice.
When creating an invoice, the `merchant_id` field is required and must reference a valid sub-merchant under your partner account.
For an advance to be taken on the invoice, a PDF of the invoice must be uploaded and the associated customer must be approved and have available credit for the amount of the invoice.

 - [GET /invoices](https://docs.resolvepay.com/partners-api/openapi/invoices/listinvoices.md): Return a list of invoices across your sub-merchants.
 - [POST /invoices](https://docs.resolvepay.com/partners-api/openapi/invoices/createinvoice.md): Create a new advanced or non-advanced invoice for a sub-merchant with the desired terms. The `merchant_id` field is required and must reference a valid sub-merchant under your partner account.
 - [GET /invoices/{invoice_id}](https://docs.resolvepay.com/partners-api/openapi/invoices/fetchinvoice.md): Retrieve an existing invoice by its ID.
 - [PUT /invoices/{invoice_id}](https://docs.resolvepay.com/partners-api/openapi/invoices/updateinvoice.md): Update an invoice.
 - [DELETE /invoices/{invoice_id}](https://docs.resolvepay.com/partners-api/openapi/invoices/deleteinvoice.md): Delete an invoice.
 - [PUT /invoices/{invoice_id}/send](https://docs.resolvepay.com/partners-api/openapi/invoices/sendinvoice.md): Send an invoice to the customer.
 - [POST /invoices/{invoice_id}/void](https://docs.resolvepay.com/partners-api/openapi/invoices/voidinvoice.md): Void an invoice.
 - [POST /invoices/{invoice_id}/cancel](https://docs.resolvepay.com/partners-api/openapi/invoices/cancelinvoice.md): Cancel an invoice.