What happens if you don't declare forex profit in Mexico

How SAT spots an undeclared account

Beyond the automatic exchange of account data covered in the tax article, SAT has a domestic tool: the discrepancia fiscal. Under Article 91 of the Income Tax Law, an individual can be put through this procedure when their erogaciones in a calendar year exceed the income they declared.^[1] Erogaciones are defined broadly, and expressly include deposits into bank accounts, financial investments and credit cards.^[1] A broker paying your withdrawals into your Mexican bank account is exactly such a deposit, so undeclared trading profit is what this check is built to surface.

The gap is treated as income

When the erogaciones exceed declared income, the difference, net of what you declared, is presumed to be omitted income taxed as “other income” under Chapter IX, the same bucket as a trading gain, at the ordinary rates of Article 152.^[1] Before that, the procedure gives you a chance: SAT notifies the discrepancy, and you have 20 days to explain in writing and prove the origin of the money.^[1] This is where the broker's statements matter: if a deposit is your own capital coming back, or income you already declared, showing it closes the gap. What you cannot document is what gets taxed.

What it costs on top of the tax

Paying late is never just the tax. The amount owed is first updated for inflation, the actualización, by the consumer price index,^[2] and then carries recargos, surcharges owed to the treasury for paying after the deadline, running for the whole period of delay.^[2] Those two apply even in the mildest case, a simple late payment.

The fine

If the shortfall is uncovered by SAT exercising its powers, rather than fixed by you first, it also carries a fine of 55% to 75% of the omitted contributions.^[2] That is charged on the tax itself, on top of the updated amount and the surcharges.

In practice: it is almost always money, not prison

The criminal end is worth putting in its place, because the distance between “I under-declared” and “I go to prison” is wide. What normally comes first is a notice from SAT asking you to clarify or correct, sometimes a carta invitación, not a criminal case. A discrepancia you do not clear up within the window ends in an assessment of the omitted tax: a tax bill that gets paid (the tax, the actualización, the recargos and, where it applies, the fine). That is the ordinary outcome for an individual.^[3]

The crime of defraudación fiscal sits at the very top of the scale and requires deceit or taking advantage of errors, not a simple oversight. It is true that the Code assimilates to those same penalties anyone who reports “income lower than what was really earned”, and that prison runs from three months to nine years depending on the amount.^[2] But the criminal route is used sparingly and concentrates on large, deliberate fraud, above all by big taxpayers: the Article 108 prison thresholds start in the millions of pesos, and nationwide the criminal complaints for tax offences run to a few hundred a year and the convictions to dozens.^[4] This is the end reserved for deliberate concealment of large amounts, not an honest late filing.

The cheap way out: fix it first

The Code leaves a clear exit. No fine is imposed when you meet the obligation spontaneously, that is, late but on your own initiative, before SAT has discovered the omission or notified an audit or any requirement.^[2] In practice that means filing a corrected annual return, a declaración complementaria, and paying the tax with its actualización and recargos: you still pay those, but the 55% to 75% fine falls away and you stay clear of the criminal side. Once SAT has moved first, that door is closed, which is the whole argument for declaring on time, or fixing it before they ask.