Peter's PR man, our first point of contact, simply ducked for cover. He even changed his email address. Before decamping with the speed of a bank transfer to Bermuda, though, he did respond to one question. Does Xstrata pay tax in Australia? ''We pay tax and royalties in Australia,'' he said. Ah yes, the stock PR line. But a royalty is a thing you pay for the right to extract minerals from somebody else's soil. How about income tax? Not a peep. At least the ''communications'' operatives from Shell and Google, when confronted with hairy tax questions, had the decency to have an argument. This bloke just hid. But early on Friday we finally stumbled upon a fair-dinkum set of financial accounts, and our questions were partially answered.

Lo and behold, Glencore had booked cash of almost $15 billion from coal mining in Australia in the past three years and had effectively paid zero tax. They make roughly $5 billion a year from copper, zinc and nickel too, but we'll stick with coal today as it would take another two weeks to dig out the rest of the accounts. Anyway, the boys from Zug - the Swiss tax haven from which Glencore sprang - did actually pay some tax. They managed to ''leak'', as they say in the trade, just $507 million in income tax, on cash receipts of $30 billion. That's roughly 1.7 per cent leakage in seven years. Tax is levied on profits, or course, not on sales. Cash is more relevant though, since multinationals engage in the practice of transfer pricing; that is, siphoning profits out of this country, where the corporate tax rate is 30 per cent, into more tax-amenable jurisdictions. Here they were, drowning in cash - the biggest coal boom in history was in full swing - but what does Glencore do? It borrows billions from its parent and other associates overseas and pays them interest on these loans of $1.4 billion. That's flair for you. Get the money out, and saunter off with a tax deduction on your interest payments to boot. And that is just profit shifting via a few loans. Of Glencore's $4.3 billion in sales last year, some $1.97 billion worth were made to related parties.

Fancy footwork During the quest to get a straight answer from Glencore and Google these past weeks, Australia's first-quarter GDP figures arrived. It was a nice set of numbers, to which mining exports were said to have lent a fillip. The economy is expanding at a respectable 3.5 per cent annually. In the first 10 months of the financial year, we shipped $64.3 billion in iron ore. What is harder to track is how much GDP growth you can have without the cash. Multinationals are past masters at controlling a supply chain and siphoning cash at every point.

Consider an iron ore sale from an automated mine straight to a conveyor to a ship chartered by the parent company in a tax haven. The parent - let's say an office in Luxembourg - will keep the transport fee and the margin on the ship charter. The marketing fee may go to an associate - let's say in the Swiss town of Zug, where Glencore started life and BHP also has offices. Then there is the interest margin on borrowings used to fund the mine. Actual dividends may be sent off to another related party - perhaps in London - who may also resell the iron ore in transit at a handsome margin. The royalties stay, along with a hole in the ground. Thank heavens for the royalties. A tweak to corporations law a couple of years ago meant dividends do not have to be paid out of profits but may be sourced from cash (sheltered by non-cash deductions such as depreciation) and can come out of capital (therefore tax deferred). Tax is only payable when the parent sells its shares in the Australian entity.

All this is merely leakage from the cash-flow pipe, a practice in which Glencore Xstrata is a past master. Crying shame There is a new breed of tax avoider on the block, and they make Xstrata look like a half-decent corporate citizen. Google has now refused to respond to questions about its accounts for two weeks. Instead, its head of Australian operations, Maile Carnegie, has done a feel-good magazine interview lamenting the ''shaming'' of multinationals. The line from Google is they are acting within the law. If so, why hide from questions?

We await a response.