In Mexico, the SAT Tax Authority monitors a wide range of financial transactions by collating data from banks, notary deeds, electronic invoices and other sources. Goal — identify cases where actual expenses and assets do not correspond to declared income. At the same time, SAT does not have the resources for total control: monitoring is carried out selectively, mainly when large amounts or significant discrepancies in data are detected.
We would like to remind you that the subject of taxation in Mexico is all income received in Mexico, as well as business income received from abroad, regardless of the chosen tax regime — read thispublication. In addition, there is an obligation to declare the purchase of a car or real estate. Failure to declare income, if any, or purchases is already considered a signal for SAT.
One of the key areas of focus for SAT is the purchase of a car. Vehicle dealers are a regulated activity under anti-money laundering legislation. When completing a transaction, the buyer reveals identification data, proof of address and income information. Materials are transmitted to SAT and, if necessary, to Financial Intelligence Unit (UIF). Expensive cars — under close scrutiny. If the car's tariff significantly exceeds the buyer's officially declared income, this may trigger an audit. The fact of purchasing a vehicle is subject to mandatory reflection in tax reporting, since SAT considers it as an indicator of income level.
In addition, the purchase of real estate is placed under special control. Notaries and banks are required to provide SAT with information about real estate purchase and sale transactions. This data is compared with income information from employers, credit institutions and other sources. If there is a significant discrepancy between the declared income and the price of the acquired property, a request for information about the origin of the funds is possible. The purchase of real estate is also subject to mandatory declaration — both when purchasing with your own funds and when using a mortgage loan.
SAT also tracks bank account transactions. Aggregated data is disclosed by banks and the Commission on Banking and Securities (CNBV) — without total tracking of each purchase, but with the prospect of seeing the total amounts and dynamics of expenses. SAT compares your annual expenses with your returns: specifically, if you officially earn 20,000 pesos per month, but consistently spend 50,000 on cards, the system flags this as a «fiscal imbalance» (discrepancia fiscal). If the difference is significant, SAT is able to issue a notice requesting clarification. Unless you can prove that the difference was made up by, say, old savings, gifts or a loan, it will be counted as additional income subject to tax.
Expenses include, but are not limited to: credit and debit card purchases, payments for services and subscriptions, transfers between accounts (including international), car or real estate purchases, and large cash deposits.
Particular attention is paid to electronic invoices (CFDI). All income must be supported by invoices. The SAT records discrepancies between issued CFDIs and declarations. If an entrepreneur or individual has an obligation to issue invoices, but does so partially or untimely, the system automatically detects discrepancies between the data.
When an entrepreneur receives income through electronic platforms (Uber, Didi, Airbnb, Mercado Libre, Amazon, Rappi, or any online services where users sell goods or provide services), part of the tax reporting for him is automatically created by the platform itself and sent to SAT. If the entrepreneur subsequently files a return that does not mention this income, SAT will instantly see the discrepancy: the system already has an electronic invoice confirming the receipt of money.
Cash deposits into bank accounts are also controlled. Banks are required to inform SAT if a customer deposits more than P15,000 in cash per month (cumulative across accounts). Depositing cash above this threshold is not illegal and does not automatically result in tax on the funds deposited, but may provide the basis for an analysis of the source of funds. If the amount of deposits exceeds declared income, SAT can initiate an audit, but only does so for very large amounts.
To summarize, SAT can collate information about a taxpayer's income and expenses from different sources. Key signals for permissible inspection — large purchases, regular discrepancies between expenses and income, large cash deposits and lack of adequate tax documentation.
At the same time, the system does not imply constant monitoring of each taxpayer. Control actions are launched only when significant deviations are detected or based on the results of an analytical sample. Most audits begin with a notification of discrepancies and a request for clarification. If there are supporting documents, sanctions will not apply.