I am finding a fast-track bill in my invoices folder - how come, I did not order fast-track?

Under invoices, there may be a pro-forma invoice for authors who wish to fast-track a paper. See How to fast-track (expedite) a paper and what are the benefits? 

The invoice is automatically generated for all submissions in case authors require an invoice before their institution can pay.

The invoice can be ignored if authors do not wish to fast-track their paper.