If you keep a Mexican pre-pay SIM card alive between trips, time is running out. A law enacted on January 9, 2026 required every Mexican cell phone number to be registered to a verified person, but by late June fewer than half of all lines had signed up. The government has since scaled the rules back — and changed the deadlines.

The big change: if your Mexican number is on a monthly contract, you no longer need to register at all. The obligation now falls only on pre-pay (pay-as-you-go) users, whether you hold a physical SIM or an eSIM, and whether you're in Mexico or abroad.

Disconnections are now staggered between August 15 and December 31, 2026, based on the last digit of your phone number. Numbers ending in 0 face a cut-off on August 15; each subsequent digit buys roughly two more weeks, with numbers ending in 9 disconnected on December 31. A disconnection isn't immediate cancellation — your line comes back once you register — but providers may eventually retire numbers left unregistered.

Registering is straightforward. Mexicans can use their INE card or passport; foreigners need a valid passport, and legal residents will have it matched automatically to their CURP. You can register through your provider's official website (uploading a photo of your ID, and possibly your phone's IMEI number) or in person at a service centre. New pre-pay lines must be registered within 30 days of activation — and for tourists buying a local SIM, that registration happens as part of the purchase.

A few exemptions worth knowing: foreign phone numbers roaming in Mexico don't need to register, landlines are unaffected, and home internet modems on contracts are generally excluded. The big three providers are Telcel, AT&T Mexico and Movistar — and it's worth ignoring any registration links that arrive by SMS, email or social media, since scams are an obvious risk with a rollout like this. Go directly to the provider's official site.

For anyone who keeps a Mexican number for WhatsApp, banking codes or family contact while living abroad, this is the practical takeaway: check whether your line is pre-pay, find your number's last digit, and register before the matching cut-off date. Personal data is held by the phone companies under Mexican privacy law, though the government can request access through due legal process.