FED up with parents who fill in their children's identity card (NRIC) numbers wrongly, freelance writer Gangasudhan Bala Supramaniam, 32, hit upon a solution.

Last month, he invented a service to check whether the seven digits and letter in an NRIC number were legitimate each time he handled paperwork for the Singapore Indian Development Association's student-tuition programme. He is a volunteer with the organisation.

Based on the 'Modulo 11' algorithm that the NRIC system follows, his invention allows users to download a Microsoft Excel spreadsheet from his blog, key in the NRIC number, and let the system confirm its legitimacy.

In Mr Gangasudhan's case, this ensures the students' NRIC numbers are valid before he registers them for classes. my paper understands that the system is legal. IT security expert Aloysius Cheang said the formula is common knowledge among those in the industry.

The checker can help verify the NRIC numbers before access is granted for further online transactions.

Said Mr Cheang: "When used appropriately, this can be a useful first-level protection against malicious attacks."

Administrative executive Charulatha Vengadiswaran, 31, has also benefited from the free service.

She said: "The NRIC-checker helps cut down the time I spend chasing people for official documents."

The Immigration and Checkpoints Authority has a similar service called iCheck.

Available online, it needs the enquirers' personal information first, such as the NRIC number and issue date.

Then, the NRIC number, issue date and birth date of the identity being checked must be provided "to prevent frivolous use".