Combined Excise Return?

I received a letter that I should file my combined excise return, even if there was no activity. 

 

I do contractor work for other businesses (office administrating, scheduling, planning, paperwork, billing, etc.)


I looked through it and it looks like most of the taxes are applied to specific things like tobacco, alcohol, gambling, etc.

 

What I do is just simple contracting office work, so I’m unsure if it applies to what I do.

 

If it doesn’t, do I just check no activity?

If it does, which category do I fall under?