A little quietly, the good ship HMS Tycoon Tax slid off the policy speculation slipway and into the waters of the real world* with the start of the tax year earlier this month.

The full details are over on the official HM Treasury website of how the March 2012 budget announcement has now become law. In short, the ability of rich people to end up paying only a very low rate of income tax on their earnings by claiming huge sums in various tax reliefs has been ended.

The original idea was to introduce a mandatory minimum effective tax rate, but this was quickly swapped for a different approach to the same end – rather than enforcing a minimum tax rate, instead cap the reliefs which can be claimed and raise the effective tax rate that someone pays that way instead. (The effective tax rate being the tax they pay as a percentage of their total income.)

The big controversy previously over it was whether claiming tax relief on charitable donations would be in the cap. They’ve ended up being excluded, so very rich people can use large charitable donations to depress the effective tax rate they pay. However, they are in that case giving lots of money to good causes.

It’s no surprise that Labour’s attacks on the government over the top tax rate have not mentioned this increase in taxes at the same time for the richest. What’s more surprising is that the government itself and the media have been so quiet about it.