Why am I unable to see the Cancel button on my invoice?

The following reasons explain why you might not be able to cancel your invoice:

• Your customer does not allow you to cancel invoices.
  Check your customer's invoicing rules to see whether they allow suppliers to cancel invoices they create rule is enabled.
  
  
• Your customer has processed the invoice already.
  If the invoice has an Acknowledged routing status, your customer has already downloaded the invoice document. After the customer downloads the invoice, you can no longer cancel it even if the customer lets you cancel invoices.
  
  
• You created the invoice in your customer's procurement site.
  If you create an invoice using the Create > Contract Invoice option on the Home tab of your account, you cannot cancel the invoice. Your customer's site is the source system for contract invoices, and the invoice in your SAP Business Network account represents a read-only copy of the invoice. As a result, the Cancel button does not appear for punch-in invoices.

SAP Business Network for Procurement & Supply Chain > Transaction Documents > Transaction (Invoicing)