Prefixing 0 will be mandatory for fixed-line to mobile calls from Jan 15, 2021


Department of Telecommunications (DoT ) has now made prefixing ‘0’ mandatory for all calls being made from fixed-line or landline to mobile phones with effect from January 15, 2021. This move came after the recommendations made by the sector regulator TRAI, which had arrived at this conclusion after studying the issue of adequate numbering resources.

Those dialling a mobile number from a fixed line phones without the prefix will hear an announcement. Dialling “0” before the mobile phone number was a practice followed for outstation mobile numbers before the government allowed inter-circle mobile number portability, which effectively meant that there was no trunk dialling when it came to mobile numbers and all numbers were considered local. However, from January 15, 2021, the dialling procedure for mobile phones to mobile phones will not change.

India currently functions on 10 digit mobile numbers and the series of numbers from ‘0’ to ‘1’ are reserved for special purposes. Theoretically, 800 crore numbers are possible. Up till now, mobile numbers were traditionally registered to series starting from “9”, and some combinations starting with “8”, “7” and “6”.

With these combinations, a total of 115 crore mobile numbers are available. The “9” series i.e., mobile numbers starting with “9” has been fully used. Mobile numbers starting with other numbers overlap with certain numbering plans issued to landline phones. Therefore, to create sufficient numbering combinations, the prefix “0” has been re-introduced. In addition to subscription of mobile numbers by consumers, SIM cards are also being used for machine-to-machine communication purposes.

These include use-cases such as smart meters, for which the government has already allocated a 13-digit numbering system. TRAI had also recommended that all the SIM-based M2M connections using 10-digit mobile numbering series should be shifted to the 13-digit numbering series allocated by DoT for M2M communication; at the earliest.


The decision to add the prefix will not only clear the overlap between landline and mobile phone numbers carrying the same series but will also free up numbering resources for mobile phones in the future. In the near term itself, the exercise will result in generation of 253.9 crore numbers.