The collectors initially resorted to extensive internet research to find all the sex businesses in the city – but found their computers blocked from the relevant sites.
"The first problem was that, as public officials, those pages are actually out of bounds for us," said Stuttgart tax collector Rolf Kiener. Once the necessary special permission was granted, Kiener and his colleagues were initially shocked. "It's rather eye-opening what's out there," he said.
The new tax means that all spaces in the city used to sell "erotic pleasures" will be taxed by the square metre, including strip clubs, porn cinemas and brothels.
Establishments that offer both "initial approach" and "completion" of a transaction will be forced to pay as much as €10 per square metre per month.
By that count, a 17-sqm room would cost a brothel-owner €2,040 a year. But the tax does not include bar areas, toilets and office space, so precise measurements need to be taken.
Once the establishments in question have been identified by blushing officials, they receive a letter from the local tax office.
If they then fail to provide a detailed floor-plan, Stuttgart's bravest tax men appear at the door, armed with a tape measure. In order to avoid embarrassment, they make appointments.
"You don't want to have to go there during business hours," said Kiener.
It's estimated that Germany's sex trade is worth some €14.5 billion a year.