New York City Mayor Zohran Kwame Mamdani has a message for owners of luxury second homes: check your mailbox. The city has started sending notification letters about its new pied-à-terre tax, which targets non-primary residences worth more than $5 million.

In a post on X on Thursday, Mamdani said owners of second homes in New York City worth more than $5 million should "check your mailbox," because "you've got mail," adding that the city has sent notification letters informing property owners that the new pied-à-terre tax is "coming soon." He said the revenue would help support public services, including parks, libraries and schools.

New York Gov. Kathy Hochul also endorsed the rollout in a post on X, saying working New Yorkers "already do their part" and that she ensured owners of "ultra-luxury second homes" contribute more to the city. Hochul reposted Mamdani's announcement about the notification letters, framing the tax as a way to help fund public services.

The notification letters follow New York lawmakers' approval of the pied-à-terre tax earlier this year. The measure applies to certain non-primary residences and is expected to generate about $500 million in revenue for the city. The tax will be introduced in phases, beginning with condos and co-ops valued above $1 million before transitioning to a revised valuation system in later tax years.

Mamdani has argued that higher taxes on wealthy property owners can help fund public services and address housing affordability. The proposal, however, has faced criticism from several business leaders. Amazon.com Inc. (AMZN) founder Jeff Bezos questioned whether higher taxes on wealthy individuals would meaningfully improve affordability, while Citadel founder Ken Griffin warned that policies targeting wealthy investors could discourage investment and job creation in New York.

The pied-à-terre tax has been a key part of Mamdani's broader affordability agenda and has sparked months of debate among policymakers, investors and business leaders over its potential impact on housing, investment and city finances.