India's top court on Wednesday upheld the government's policy of issuing a 12-digit identification number to every citizen, but said it can't be made mandatory for services such as bank accounts, cellphone connections and school admissions.

The Supreme Court said in a 4-1 decision that the government could use it for tax purposes and providing benefits under multimillion-dollar welfare schemes like subsidized food items and cooking gas.

Prashan Bhushan, an attorney, said private organizations couldn't ask for it because of privacy concerns.

The Indian government has enrolled more than 90 percent of the country's 1.3 billion people since it launched the scheme in 2010 linking fingerprints, iris scans and photos of citizens to the unique 12-digit number.

Banks, mobile operators and the government itself started to require identification numbers to access various services.

Rich Indians generally possessed passports, driver's licenses or credit cards that establish who they are. But the poor often were forced to rely on electricity bills, ration cards, voting cards or letters from local officials.