My start up company never paid severance pay for the last month. They were also paying 50% less for the past 3months . They are still alive (not closed down) what is the best way to get the money back?

Get money back what money?

Did you have a written contract?

Severance pay, is not required, they have no obligation to pay this

1/2 pay, unless they were paying you less than min wage, a company may change your pay anytime they want ( unless you have a contract)

So did they tell you in writing they would pay severance and pay your other 1/2 of pay??