Here comes the taxman.

New York Attorney General Eric Schneiderman has won the right to continue the state’s lawsuit against Sprint-Nextel Corp., for allegedly underpaying millions of dollars in taxes. If the courts find Sprint fully liable, the company could owe New York up to $400 million in damages.

Schneiderman’s lawsuit claims Sprint has been illegally pro-rating state and local sales taxes on its service plans based on actual customer usage instead of the full amount of monthly access charges that New York law defines as taxable.

The lawsuit alleges Sprint has underpaid New York’s Department of Taxation and Finance at least $100 million since 2005.

Since 2002, New York Tax Law has required mobile phone companies to collect and pay sales taxes on the full amount of the monthly access charges for their calling plans. For example, when a customer pays Sprint a fixed monthly charge of $39.99 for 450 minutes of mobile calling time, the law requires Sprint to collect and pay sales taxes on the entire $39.99. According to the Attorney General’s complaint, starting in 2005, Sprint illegally failed to collect and pay New York sales taxes on an arbitrarily set portion of its revenue from these fixed monthly access charges.

Sprint’s scheme is ongoing, said Schneiderman. As a result, the state claims Sprint’s underpayment of New York sales taxes is growing by about a $210,000 a week, more than $30,000 a day.

The Attorney General’s lawsuit is the first ever tax enforcement action filed under the New York False Claims Act. The Act allows whistleblowers and prosecutors to take legal action against companies or individuals that defraud the government. Fraudsters found liable under the False Claims Act must pay triple damages, penalties and attorneys’ fees. Under the False Claims Act, whistleblowers may be eligible to receive up to 25 percent of any money recovered by the government as a result of information they provide.

Sprint asked the court to dismiss Schneiderman’s lawsuit, but the New York Supreme Court ruled against the company on July 1. Sprint appealed the decision to the Appellate Division, which unanimously affirmed the July 1 ruling on Feb. 27.