Karachi, Pakistan (CNN) -- Miss your tax deadline in the United States this weekend, and you might get a nasty letter at your door. In Karachi, Pakistan's largest city, you might get Riffee and the gang. They are "transgender" tax collectors -- whose weapons include flamboyancy, surprise -- and a little lipstick.

In a move that speaks volumes about the lengths to which Pakistan is going to tackle tax evasion, Karachi officials are using Riffee - who like many people in South Asia works under a single name - and her team as enforcers with a difference. They are sent to the businesses or houses of debtors. The aim -- in this very conservative Muslim society -- to embarrass tax debtors into paying up.

Riffee -- like her tax-collector friends Sana and Kohan -- is physically a man, but prefers to be called and dress as a woman. Their job is quite simple: each morning they turn up to work and get a list of missed payments. One by one, they make house-calls, causing trouble at each debtor's home or office, trying to get them to pay up. It's not clear how effective this tactic is, but officials insist they would not do it if it did not work.

"Their appearance causes great embarrassment amongst the people," said Sajid Hussein Bhatti, the tax superintendent who gives Riffee her orders every morning.

When Riffee was a 10-year-old boy, she decided she wanted to be a woman. Since then, she says, she's endured plenty of prejudice. "We're trying to educate society and show them how we like ourselves, but if your parents don't understand you or give you respect, how can you expect other people to?"

A Pakistani court ruling two years ago gave eunuchs -- men who have been castrated -- the right to be referred to as a "third gender." Riffee believes the same right should extend to her and her friends, although they have not been castrated.

We followed them as they visit a series of electrical appliance shops. The first debtor insists there's been a mistake and the bill's been paid. The second is less amenable, so the team threaten to come back 24 hours later, half a dozen strong -- and dance in the shop. That just may be enough to get a tax bill settled.

There is a serious side though to this theatrical tactic. Pakistan's tax take is dire: barely 1 per cent of Pakistanis pay any income tax, and the government is frantically trying to increase its income -- partially to placate the International Monetary Fund. Pakistan wants to borrow up to another $5 billion from the IMF, which insists the state improves its tax collection.

The government is seriously indebted -- and only 1.9 million people in a country of 170 million filed tax returns at all last year. By some estimates 10 million people are registered to pay taxes in Pakistan; the great majority don't pay a rupee.

In a country where many say the courts are weak and the police corruptible, Riffee and the team are a last, albeit striking, resort.