The tax will be based on the amount of CO2 you emit. High cardio jobs such as construction, delivery and politiciking will get tax credits to cover the cost. CrossFit practitioners will pay full cost, possibly even an excessive penalty. There will be a standard amount, but any smartwatch meeting the appropriate govt standard can be used to itemize if you are more sedentary.

Under this tax regime as long as the homeless person makes sure to promptly file the appropriate forms each year they should not be at risk of jail time.

( Being the internet, this is all a joke )