Image copyright ALex Duval Smith

Mali currently has two rates of income tax - 30%... or 3%. Quite a difference. So the BBC's Alex Duval Smith was surprised to be offered a choice when she went to register at her local tax office in Bamako.

Outside the yellow concrete building, a man is tethering a ram to the railings. It's not an uncommon sight; he has probably just bought the animal and has an errand at the tax office on his way home.

Inside, a row of cashiers are seated behind aluminium-framed thick glass. Each has large handbag plonked on the counter. Each bag is a different colour. Mali, for all its poverty and problems, is always hitting you with moments of accidental beauty.

But the cashiers' eyes are glazed over from inactivity. The International Monetary Fund believes Mali has the potential to improve its revenue-raising by 20%. It's not happening in here.

My mission - to register as a tax payer - takes me round the back of the cashiers, to Mrs Yattara's shoe box office. She shares it with three colleagues. There's a handbag on each desk. There's a computer, too. It's used to print out pro-forma tax declaration forms. But all the data is copied in to stacks of exercise books. Some in red ink, some in blue.

Image copyright ALex Duval Smith Image caption Mrs Aissata Yattara (back right) with colleagues Kani Sissoko and Adama Fofana

I first met Mrs Yattara, a smart woman with glasses, during the annual tax census. This is when the entire staff, bearing clipboards, leaves the office to search the neighbourhood for more tax payers.

There's always one casualty - an unlucky shopkeeper who gets closed down as an example to the others. This year a soft-drink seller was presented with a tax bill of 80,000 CFA francs - that's about $160 dollars or £100 - and when he couldn't pay, they padlocked his shop. After a week he offered to pay half the amount and added a few crates of orange squash for the tax staff. Problem solved.

Mrs Yattara leads me to her boss, Mr Kante. He has an office all to himself, and offers me a seat... a seat from which I can hardly see him. Tax rule books and copies of Finance Ministry decrees are piled into turrets all around his desk. He asks me questions about my expenses as a freelance journalist. It's unnerving because he is writing things down but I can't see what.

Image copyright ALex Duval Smith

''You have the choice between two income tax regimens, 30% or 3%, which shall it be?''

''Oh well... err 3%?'' I venture. ''Three per cent it is," he says, adding: "Now we'll have to go and see my boss.''

This doesn't faze me. Hierarchy is everything in Mali. In the course of settling everyday matters I have already met the managing directors of Mali's water and electricity boards and of the post office. I imagine that it's so rare for someone to walk off the street and offer to pay income tax that the boss would want to meet that person.

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Mr Kantako's office is enormous, with chairs lining three walls. That's normal too, because in hierarchical Mali, people move around in delegations. The meeting involves a lot of niceties. Curiously, I am expected to provide the British government's position on the demands from Tuareg rebels for self-rule in northern Mali.

''Err... Britain just wants peace,'' I say, limply. All my energy is going on trying to suppress my delight at paying 3% income tax.

''Now then.'' The tax boss asks Mr Kante to brief him about my case. Both men pore over a calculator and come up with a figure of 236,160 francs ($380, £260).

''Hmm, I would like to have seen a rounder figure,'' says Mr Kantako eventually. ''And the pound is strong - I think we would like 300,000 francs ($485, £327) from you.'' He gives me the same open look as you get when buying almost anything in Mali. As much as to say: "That's my offer what's yours?"

''Oh, and we'll want that in cash,'' he says, "but you will be given a receipt."

Mr Kante offers some explanation as we go back downstairs. ''Eighty per cent of Mali's economy is informal," he says. "The government believes the 3% rate will attract more tax payers. What people don't realise is that, as things stand, we struggle to raise 1% or 2%. So this new rate represents something of an increase!''

By that reckoning, the Malian tax authorities have actually done quite well out of me.

Perhaps because I had - strangely - volunteered to pay tax, a basic sense of fairness stood in the way of the staff putting me into the 30% bracket, where perhaps I belong.

As I leave, so does the man with the ram. Except the ram remains tied to the railings.

''Monsieur!'' I call out. He turns around.

''Your ram?''

He shakes his head. "No, no, I've had to give it to them," he says matter-of-factly, and walks away.

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