Prostitution is legal in Germany, but collecting taxes from streetwalkers requires some creative efforts.

In Bonn, officials have unveiled a meter that prostitutes must pay roughly $8 into each night to get a nightly permit to practice the world's oldest profession. Freelance sex workers get an automated ticket, much like a parking slip, according to Der Spiegel. Officials say taxing prostitutes who work out of fixed locations is simple, but streetwalkers could easily avoid duties.

"It's not fair that some women who work in establishments like sex centers or sauna clubs are taxed only because we can find them more easily there," city spokeswoman Monika Frömbgen said.

Prostitution has been legal in Germany since 2002.

BUFAS, a sex worker advocacy group, called the flat fee unfair.

"We are against such special rules, and favor the legal equality of every worker, including in matters of taxes," said spokesperson Beate Leopold.

But Frömbgen contered that Bonn has a right to collect taxes, and this makes it possible.

"Communities have a bit of room to adjust their own taxes, and we are legally granted the right to levy these taxes," she said.