Alteration-CO (Alt-CO) — amend the Certificate of Occupancy for a change of use: New York City restaurant guide
NYC DOB
What it is
When the space's legal use, egress or occupancy changes (retail → restaurant, or the CO doesn't cover an eating & drinking use), DOB requires an Alteration-CO job (formerly Alt-1) that ends in a new or amended Certificate of Occupancy — not a Letter of Completion.
When a restaurant needs it
The existing CO doesn't list your use, your occupant load or exits change, or DOB answers 'yes' to any Alt-CO qualifying question.
How to apply
Your architect files the job in DOB NOW: Build; the Alt-CO qualifying questions (inconsistent with current CO, change in occupancy or use, major change to exits, change in stories, must meet NB requirements) route it to Alt-CO. A TCO can be issued when the first Alt-CO job signs off; the final CO issues when the last open Alt-CO job closes.
Documents you’ll need
- Existing CO or proof of none
- Proposed use / occupancy analysis
- Egress and occupant-load plans
- Zoning analysis
- All trade sign-offs for the CO
Good to know
Taking over a space that was already a permitted restaurant with a matching CO usually avoids this entirely — the single biggest schedule difference between a takeover and a conversion.
Official source
DOB — Certificate of Occupancy (change of use) · DOB — Job types in DOB NOW (Alt-CO criteria)
Answer a few questions about your space and get every permit in order, with a timeline, a cost range, walkthroughs, and every application filled in for you to sign with Open.
Last reviewed 2026-10-06. Guidance only, not legal advice.