Rail firms have been accused of sitting on £1.3 billion of unpaid tax and of using a loophole to fund massive increases in dividend payouts to shareholders (link below.)
http://www.rmtbristol.org.uk/2007/10/rail_firms_exploit_tax_loophol.html#more

The RMT union claimed that almost half the £1.5 billion in dividends paid out in the last five years by rail and rolling stock firms had been funded by unpaid tax.

The union said a study it commissioned by tax expert Richard Murphy showed that tax payments remained almost constant between 2002 and 2006 even though combined profits almost doubled to £810 million.

"Deferred tax is supposed to be an allowance against investment and amounts to a hidden subsidy for rail firms, but it is being exploited to increase dividends to shareholders," said Mr Murphy.

"Rail companies are hiding behind accounting rules when presenting their figures that let them suggest they're paying more tax than they are, and that means the massive hidden subsidy the tax system gives them is not apparent. It should be."