PartActivateInvoice should be used when the complete order isn't ready to be shipped, but only a part of it. This way, the invoice that's created only contains the stuff you've actually sent and the customer doesn't need to pay for something they haven't received. 

In short, if the complete order is ready to be sent, use the ActivateInvoice request. If only a part-delivery can be made, use the PartActivateInvoice request. 

If using the PartActivateInvoice request, a new pending invoice will be created for the remaining invoice rows. In the response, this new invoice will be given a new invoice number (NewInvoiceNo). When it's time to activate the remaining invoice rows you can use either the ActivateInvoice or the PartActivateInvoice request, depending on if everything's ready to be shipped or not. Please note that the request should use the NewInvoiceNo value and not the original one. 

This method is available in the following countries:  
Input Parameters:

Field nillable Max Type Description
Username false 50 string The username used to authorize the request.
Password false 50 string The password used to authorize the request.
StoreId true 4 short The StoreId used for identification of store.
CorrelationId true 50 string CorrelationID is sent back in the response.
CountryCode false 2 string The country code (ISO 3166-1 alpha-2) for the country.
InvoiceNo false 50 string The InvoiceNo previously returned in AddInvoice.
ArticleList false - Article list The list of articles that should be activated.


Output Parameters:

Field nillable Max Type Description
CorrelationId true 50 string CorrelationId from the request if any.
NewInvoiceNo true 50 string The new invoice number with the articles that where not yet delivered.
PaymentReference false 50 string The Reference that should be as a reference on an invoice.
LowestAmountToPay false 6,2 decimal The lowest amount to pay on the invoice.
TotalAmount false 6,2 decimal The total amount to pay for the invoice.
DueDate true   datetime The due date of the invoice.
InvoiceUrl true 200 string The url to invoice in pdf format.