US tax Sch C for booking engine ?

Curious, fellow Americans, how do you classify the cost of your booking engine, online reservation services on Schedule C?
Advertising? Office expense? ??

I will have to ask my magician. She just got my stuff today. Oh, I just realized - that is all in the cc payments category, not separated out. I will have to ask how she wants that part.... Thank for the question.

I categorize it as advertising.

i always considered it cost of doing business for office expense. i did not consider it advertising because i used it. that was before the online stuff existed though. i see advertising more like paying for directory listings, etc.

We have a section for professional associations, which included directories and reservation programs. Office/Business expense.