What happens if you overstay your visa in Mexico?
What happens if you overstay your visa in Mexico? Extensions and renewals. The visitor permit cannot be extended or renewed; and you must leave Mexico by the date it expires. If you over-stay your visitor visa you will need to pay a fine when you leave the country.
What happens if a US citizen stays in Mexico longer than 6 months?
If instead they wish to stay longer than 6 months, they may have to apply for a new visa or leave the country temporarily and obtain a new FMM as they return to the Mexican border. Keep in mind that visitor visas do not allow the traveler to undertake paid work while in Mexico.