Capital Gains Tax

In Mexico, the concept of capital gains tax does not apply in the sense in which it is determined in the United States. Here, the gain from the sale of the property is considered as normal income at a tax rate of up to 30%. In order to determine the gain, the following costs and expenses are deducted from the amount for which the property is officially sold:

Deductions 

The original land cost and the depreciated construction cost, based on the number of years the property was held and adjusted for inflation according to the official consumer price indexes.
Additions, modifications and improvements, but not maintenance, made on the property (construction), adjusted as above.
Commissions paid to real estate brokers by the seller.
The closing costs, including all expenses, taxes and fees paid by the seller.
The Notario will retain the calculated gain after deductions forwarding it to the Mexican tax authorities.

The seller will then deduct this amount against his her annual tax return, which becomes an adjustable tax credit in the U.S.

On the other hand, there is no capital gain tax in Mexico if there is conclusive proof the seller has had the property as his primary residence for the previous 5 years

It is VERY highly recommend that before selling any property in Mexico that you consult an expert.