accessory apartment

What is the name of your state (only U.S. law)? new york i bought a house 26 years ago with a mother daughter apt.now the town says i have to file the paperwork to make it legal.is there any type of grandfather clause for this type of situation?

was the original build where the apartment was created all permitted properly at the time?

point of clarification:

were the proper building permits obtained to build the apartment?

accessory apt.

i dont believe any permit was required when it was converted. the original house was a summer -vacation home built in 1940 or so. over the years it was added on to make it larger.eventually it became a full time residence. i have not changed anything since i've owned it.this was a common practice in this area to make mother daughter apt's and house was sold with such in the closing documents.

Have you asked them to send to you a copy of the actual ordinance that they are using to back this up? If it was me I would , reason being is to see what the begining date is and so you can see if there is a older code that applys to the property, example, I know of a city in 1976 that no longer allowed houses that were remodeled into two units like a up /down to have just one door with one set of stairs for egress. So all the older upper units that only had one door could stay that way. Some community librarys actually have town code books available too as well as some citys selling them. Learning your towns ords will help prevent surprises , you also might want to learn what they will require if you were to convert to a SFH someday. this way you will know if you fall under a newer full code compliance or not also you may want to see if your town has ords that spell out underwhat conditions the structure cannot be rebuilt as it is incase older ords allow the unit to be as it is but the structure becomes damaged by fire or weather , they might have a actual percentage formula like say 50% destroyed and then all they will allow is SFH to replace it.