The Toronto Transit Commission is reminding customers they have until the end of February to exchange their old tokens for new ones.

The TTC hopes its new token, resembling the bi-metallic toonie, will thwart counterfeiters, so it has ordered about 20 million new tokens at a cost of $1.7 million.

Mike Butler, the TTC's superintendent of investigative services, says a number of people with large amounts of fake tokens have already been charged trying to exchange them.

He says some people have tried to bring in hundreds of tokens at a time.

"Some people have legitimate excuses so there are no charges laid, but there have been a couple of people charged and arrested."

Butler says 20 to 30 per cent of the tokens recovered by the TTC will be bogus.

He says the new discs should remedy the problem because they're virtually impossible to counterfeit.

Last week, a Toronto woman pleaded guilty in a U.S. court to taking part in a U.S.-Canada counterfeiting operation involving TTC tokens. More than two million bogus tokens were produced by a legitimate Massachusetts mint, the trial was told.