Pulled this from Canada smart website because you didn't specify kms or age from in service:
I couldn't tell what model year you have so I just chose 13.
Starting on page 65 lists the services that need to be done. Page 75 lists additional work to be done. (They could have made it simpler to understand, I know.)
So every year or 15k km oil change. It seems every year you should change the combination/cabin air filter.
Every two years or 30k km brake fluid change.
3 years or 45k km replace engine air filter and spark plugs
4 years 60k km replace coolant
6 years 90k km replace poly-v belt and check/correct valve clearance.
For years or km it's which ever comes first.
I'd change the cabin air filter on my own, unless you have some sort of back problems/physical issues which may not allow you to bend down into the footwell to reach it.