ISABI (Impuesto Sobre Adquisición de Bienes Inmuebles — ISAI in several states) is the acquisition tax the buyer pays when property changes hands in Mexico. Each municipality sets its own rate; across the country it typically runs 2% to 4.5% of the transaction or appraised value, whichever is higher.
In practice
The notario calculates it, withholds it from closing funds and remits it to the municipality. You never file it yourself, and it is not negotiable. It is the single largest line in your closing costs, which across the Riviera Maya typically total 6–8% of the purchase price once acquisition tax, registry fees and notario fees are added together.
Because the rate is municipal, it changes from one town to the next inside the same state. Ask the notaría for a written closing-cost breakdown before you sign, with ISABI already calculated on your specific transaction. Until the tax is paid, the deed cannot be recorded at the Registro Público de la Propiedad — so it is not an optional line.
This tax is one-time. The costs that repeat every year — predial, maintenance, the bank trust annuity — are a separate budget, and land is treated the same way as a built home: the base is the value, not the type of property.
Watch out for
Anyone offering "closing costs included" without a line-by-line breakdown. That is not a discount, it is a number you cannot verify. What ISABI actually costs depends on the value declared in the deed, which is why the breakdown and the avalúo belong in the same conversation.
Related: Avalúo · Predial · Escritura · What owning property in Mexico costs each year