According to a Development Authority of Singapore (IDA) statement, the amount was for a tax provision "mistakenly included in the S$1.5 billion compensation paid to SingTel".
The compensation was paid in March 1997 for damages caused by the loss of its expected seven-year monopoly from 2000 to 2007.
To date, SingTel has failed to pay back the amount, the regulator said.
SingTel, on the other hand, has stood firm against the charge. In a statement to the Singapore Exchange, the telco said it "disagrees with IDA on its entitlement to the money and will be defending the claim".
