billing Cycle dates

I'm trying to add months using Add.months function in power query and same time I'm trying to subtract one day from the result. How can I do this ?

Foe example Billing Cycle starts from 2/15/2020 and ends on 3/14/2030. In my case I have start date and billing period qurterly/annually.2 year. How can I do this with out adding additional step in power query