Three New Yorkers are suing Mayor Zohran Mamdani over New York City's rollout of the new pied-à-terre tax, seeking to have roughly 17,000 notices to property owners declared null and void. The suit does not challenge the tax law itself, but alleges the administration violated state notice requirements and caused confusion by publishing a list of nearly 1 million properties that might face the surcharge before narrowing the pool. City Hall says state law required the list and has extended the deadline to seek an exemption until September 18. The levy, passed in May, applies to second homes valued above $5 million and co-ops and condos valued above $1 million that are not used as primary residences, and is projected to raise about $500 million a year.