I WANT to look at a few things that have passed across my desk in recent weeks.

Each demonstrates that tax rules can produce some unexpected results – and occasionally shocks.

One thing you might think is obvious is the date on which a transaction takes place.

This is particularly important close to the end of a tax year or a company’s accounts year as it can affect both the tax rate and the date the tax falls due.

Just after Christmas I spoke to someone who expected to pay capital gains tax in January 2015 on a land sale because they had completed the sale in the current tax year.

Unfortunately they had exchanged contracts a few days before the start of the current tax year.

For capital gains tax (CGT), the date of exchange, not the date of completion, is generally the critical date.

As a result the tax in this case was payable in January 2014, a year earlier than expected.

The news came as a shock.

I also recently spoke to someone who was giving a property to his wife.

He said he knew that there was no CGT, inheritance tax or stamp duty land tax to worry about.

I asked if there was a mortgage on the property.

It turned out that there was and because of that there would be an unexpected stamp duty land tax liability on the transfer.

Another shock.

Someone else I spoke to has two stockbrokers.

One broker is always told to use the annual CGT allowance in full and the other is told that it has been used elsewhere.

Both produce detailed capital gains tax reports.

The problem is that there are holdings of some major blue chip stocks such as Vodafone in both portfolios.

Looking at the portfolios – and tax reports – individually gives the wrong answer for CGT because the complex share “pooling” rules have to be applied to the total holding of each stock.

Yet more shocks.

*Paul Aplin OBE is a tax partner with A C Mole & Sons and chairman of the Technical Committee of the Institute of Chartered Accountants in England & Wales Tax Faculty; you can follow him on Twitter @PaulAplinOnTax.

He and fellow tax partners Amanda Gunter and Paul Kingdom can be contacted on 01823-624450.