Before you start

A CURP, from which the RFC is generated
Work-authorised status if you will be on a Mexican payroll
A comprobante de domicilio under three to four months old
Passport and resident card

Step-by-step

1
Register the RFC
Inscribe yourself in the Registro Federal de Contribuyentes on the SAT portal using your CURP, or at a SAT appointment with ID and proof of address. Salaried people register under sueldos y salarios; your employer can also register you in bulk.
OnlineWho: You or your employerOften under an hour onlineFree
2
Get the e.firma and the Constancia de Situación Fiscal
The e.firma needs one in-person SAT appointment with fingerprints; the Constancia downloads instantly afterwards. HR, banks and landlords all ask for the Constancia, so treat it as a document you refresh rather than a one-off.
In personWho: YouOne appointmentFree
3
Hand HR the RFC and let payroll withhold
Your employer calculates and withholds ISR from every payment, remits it to SAT and issues a payroll CFDI. The withholding appears on the payslip and nothing separate is paid by you.
Via employerWho: Your employerFrom the first payroll run
4
If you are independent, check whether RESICO fits
The Régimen Simplificado de Confianza taxes an individual's gross receipts at 1% to 2.5% of ISR, on a band scale, up to an annual ceiling of MXN 3.5 million, with monthly filings and no deductions. It must be elected — registering on autopilot puts you in the general regime for the year — and crossing the ceiling drops you out of it from the following month.
OnlineWho: Self-employed individualsElected at registration or at the start of a year
5
Understand what actually makes you a Mexican tax resident
The day-count rule people repeat is not the Mexican test. Article 9 of the Código Fiscal de la Federación turns on where your casa habitación is; if you keep a home on both sides of the border, Mexico looks at your centre of vital interests, deemed to be here when more than half your income for the year is Mexican-source or when the main centre of your professional activities is in Mexico. For someone splitting time between Monterrey and Texas that is a question about houses, families and income sources, not nights. The separate 183-day figure is a treaty and non-resident-employment concept. Speak to a cross-border accountant early.
OnlineWho: You
6
Pay predial to your municipality
Property tax is municipal. San Pedro Garza García, Monterrey, San Nicolás and Guadalupe each set their own rates and their own early-payment discounts, generally largest in January. San Pedro's rates are among the highest in Mexico and its services are correspondingly good, which is a trade to make consciously.
OnlineWho: Property ownersAnnually, discounted early in the year

Documents you’ll need

CURP
Passport and resident card
Comprobante de domicilio
RFC, Constancia de Situación Fiscal and e.firma
Annual withholding summary from your employer, or the CFDIs you issue

Things most newcomers don’t know

Monterrey's border economy means an unusual share of residents owe two tax authorities.

United States citizens and green-card holders are taxed on worldwide income wherever they live, and must file with the IRS and report foreign financial accounts regardless of Mexican withholding. In Monterrey, dual nationals, people with Texas property, and cross-border consultants are common rather than exceptional. Assuming Mexican payroll withholding is the end of the matter is the single most expensive error in this city's tax landscape.

Source: IRS / PwC Worldwide Tax Summaries

RESICO is the most useful regime a Monterrey freelancer can know about, and it must be elected.

The simplified regime taxes gross receipts at 1% to 2.5%, up to an annual ceiling of MXN 3.5 million, with straightforward monthly filings and no deduction bookkeeping. For a consultant invoicing industrial groups it is dramatically lighter than the general regime. Because it has to be chosen at registration or at the start of a year, people who register without advice frequently spend twelve months in the wrong regime before anyone notices.

Source: SAT

Nuevo León taxes employers and property, not payslips.

The state's 3% payroll tax is borne by the employer and never appears as a deduction on an employee's salary, and Nuevo León is not one of the states levying a cedular tax on rental income. What reaches residents personally is municipal predial, which varies enormously — San Pedro sits at the top of the national range with services to match, while neighbouring municipalities charge a fraction for the same nominal service.

Source: Gobierno de Nuevo León

Most single-employer salaried people are not required to file at all.

ISR on salaries is withheld at source and reconciled by the employer at year end. With one employer issuing proper payroll CFDIs, income under MXN 400,000 and nothing extra owing, no annual return is required — which newcomers from filing cultures find hard to believe. The reverse is the trap: a second employer in the same year, or crossing that threshold, makes filing compulsory even though tax was already withheld.

Source: SAT

Common mistakes to avoid

Assuming Mexican withholding discharges a US or other home-country filing obligation.
Registering in the general regime without checking whether RESICO applies.
Splitting time with Texas and assuming a day count settles your tax residency — Mexico asks where your home and centre of vital interests are.
Letting the four-year e.firma lapse.
Missing the January predial discount, or paying to the wrong municipality.

Some of this may be out of date. Spotted something inaccurate? Help us keep it right for the next newcomer.