Why is there an invoice for the fast-track/expedite fee? I didn't order this!

A pro forma invoice for the optional fast-track fee is always automatically generated for each submission, for authors who need to submit an invoice to their finance office. 

The fast-track fee is optional and the invoice can be ignored if you do not require a decision within 4 weeks (20 business days).

See also:

• How to fast-track (expedite) a paper and what are the benefits?