Should you put Aim shares in your Isa? So what are the pros and cons of the new rules? Firstly, the latest move actually makes Aim shares one of the most tax-advantaged of all investments. In most cases, they are already exempt from inheritance tax. From next year, investors won't have to pay stamp duty on Aim stocks. And the new rules now add income tax and capital gains tax exemptions to the list of benefits. So investing in individual Aim shares makes sense from a tax perspective but should investors really be picking stocks themselves in the alternative market? What are the risks of Aim investing? The principal concern is that the listing requirements for Aim shares are less strict than for companies on the main market. For example, they can get away with a shorter track record of audited results. That makes Aim an attractive market for young, unproven companies but can increase the risks for investors. Aim has also tended to attract a fair proportion of small companies in the riskier technology or natural resources areas of the market. Again, this can mean potential gains but a significant risk of loss too. For some investors that is a chance they are happy to take, perhaps with just a small proportion of their overall portfolio. But for many, perhaps most, investors, it's not a risk they need to take. That's because the inability to hold single Aim stocks within an Isa has never stopped investors gaining an exposure to the alternative market in a tax-efficient way. Smaller company funds holding Aim stocks have always been eligible to be held in an Isa. The Fidelity UK Smaller Companies Fund currently holds between 15pc and 20pc of its holdings in Aim. The need to tread carefully with Aim is demonstrated by the market's performance over the years, which has been volatile. Since the market rally began four years ago, Aim has outperformed the FTSE 100 slightly but it has been a white-knuckle ride. To start with, Aim outperformed by a wide margin but its exposure to underperforming natural resources stocks has, in the past couple of years, seen it fall short. In the good years leading up to the crisis, Aim was the place to invest but 2008 was a shocker - the market lost around two thirds of its value that year. Aim is stock market investing that's red in tooth and claw. The winners - such as Asos, up from 3p in 2003 to £46 recently - have made fortunes, but there have been big losers too. I think it is only fair that investors can now invest in Aim stocks in a tax-efficient way. But they need to keep their eyes wide open. Tom Stevenson is investment director at Fidelity Worldwide Investment