Massachusetts is introducing a new tax withholding requirement that will reshape how many high-end real estate closings are handled—especially in Brookline, where million-dollar sales and non-resident owners are the norm. Beginning November 1, 2025, any $1M+ sale involving an out-of-state or international seller will require a portion of the proceeds to be withheld at closing and sent directly to the Department of Revenue. It’s not a new tax, but it does change the timing dramatically, and in a market with a globally diverse ownership base, this rule will surface often. Understanding how the withholding works, who it applies to, and how it affects your net proceeds has become an essential part of preparing for a Brookline sale in 2025 and beyond.