They Pork Pie.

From the bottom to the top, from the small to the big, lying is habitual and endemic in the tax office.

Let's start big: when HMRC lost bank and personal details of 25 million customers in November 2007 they blamed the loss on a junior member of staff at their Washington office. "Who?" asked The Guardian, and “are they still in work?"

The answers seemed complex and contradictory. Some statements said that the employee was still in work, some said they were fired and some simply said, "It's irrelevant." The Daily Mail detected this porky and ran the headline, "Bungling junior official who lost benefits discs 'is being made a scapegoat'.

A few days later the truth came out. It became clear that the discs had actually been lost by a career civil servant and the data hadn't been edited as it should have because of cost-cutting. The Telegraph said, there had been a cover-up. Which is a nice way of saying: HMRC has been telling us a pack of lies.

At the other end of the scale, when HMRC opens up a small Self Assessment investigation it's standard to go through all the expenses claimed and say, "You can't have that!" and "You need to make a deduction for personal use!" [see point six in what HMRC don't want you to know].

The idea of reducing expenses is to increase levels of tax. In their Code of Practice HMRC say they want you to pay the right amount of tax, "No more and no less than you should." But this is a lie - quite simply investigators are told that they need to get results - that's what they set out to do.

In my case expenses were slashed from £5,000 to £1,000 in a heartbeat. After six months of negotiation we settled on £3,000. So was it not deceitful to disallow so many expenses when they were valid? Was it not a lie? No, the HMRC line is that they can't be wrong, they will simply say, "I saw X and I didn't think it was valid, you explained why it was and I accepted that."

The result of this policy is that you can spend - as I did - nine months arguing over something that is worth only a few pounds in tax. It's an expensive and exasperating process where you are forced to dig your heels in just to hold on to what you have. Most people - particularly those who are unrepresented - give up and throw in the towel - and that (as you might imagine) suits HMRC down to the ground.