Good question. What building is it? I found this from a Google search but I'm not sure how to interpret it:
"In 421-a buildings, where the tax benefits are for 10 or more years, and provided that a “2.2%
lease rider” is offered by the owner and signed by the tenant, owners can collect annual “421-
a” surcharges equal to 2.2% of the rent charged at the beginning of the period of gradual
diminution (when real estate taxes begin being phased in)."
from
https://hcr.ny.gov/system/files/docu...SHEET%2041.pdf
Kinda makes it sound like it's not mandatory? But I'm not sure. I'm hoping for a 421-a building myself, and definitely don't want to pay a surcharge, so I'm curious to see if someone can give a better answer.