The deadline for the first phase of registrations had originally been set for October 16 last year but the Telecommunications Regulatory Authority (TRA) decided to extend it into the new year to allow subscribers more time to register.
The scheme is part of the TRA's "My Number, My Identity" campaign, which aims to link subscribers directly with their sim card to tackle fraud.
Both du and Etisalat had begun to contact subscribers last summer via text message alerts.
Customers were supposed to be alerted in several phases to prevent a last-minute rush.
Only those sent SMS messages to re-register face the January 17 deadline. Failure to register may result in the Sim card being blocked until it is.
Customers who have received text messages can register at their respective carrier's outlets and shops across the UAE.
The process requires customers to fill in an application form and take a valid passport, residency visa and Emirates or GCC identity card.
Subscribers who have not received SMS alerts can also register by following the same procedure.