TNT may have changed its name, but it continues to be haunted by its past. The Dutch postman's ongoing tax saga has just taken another gloomy turn, knocking €500m off the group's market capitalisation. Its last annual report already hinted at further liabilities anywhere between zero and €400m, linked to past tax filings of several subsidiaries.

Now, the mail and logistics group's inquiries have revealed the likelihood of illegal acts. More worryingly, attention has shifted to several non-UK subsidiaries, which remain unidentified.

TNT appears as hard-pressed as anyone else to quantify an upper limit for potential liabilities. But, while more than 70 per cent of its sales come from outside the Netherlands, TNT still makes the bulk of profits at home. In the UK in particular previously the focus of attention by tax authorities the original €400m worst-case estimate probably would have translated into several times its local subsidiaries' annual profits.

As a major shareholder, the Dutch state can hardly be keen on causing further embarrassment. On a group level, TNT's taxes are not abnormally low. Its average effective tax rate for the past three years was a whopping 43 per cent, partly because of a previous UK tax settlement in 2003. The trouble is that the postman always rings twice and not only in crime novels. With TNT's shares still trading at a premium to rivals, it urgently needs to clarify where its problems lie.

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