Tax on investment over 10 years?

I've had an investment for around 10 or more years that originally was setup by my grandmother and is still in hers and my mothers name. It's some type of bond or managed trust. It's tripled in value over that time.

If I cash it in, will I have to pay any tax on it?

Many thanks.

As you have posted this in the UK Taxes section, I assume you desire an answer based on UK law rather than US law. i will do my best to oblige.

My first question is whether you are free to cash it in at will. If so, it is yours and you will have to consider the tax consequences. Most likely, this involves paying CGT. An asset that has been owned since before 17th March 1998 falls partly or wholly under the old rules so you would need to find indexation tables to compute the gain, as well as apply the new rules, if relevant - you would have to do that if the investment was added to (other than stock dividends or rights issues).

You will, of course, need to know the original cost or the market value on the date it was gifted to you.

If you cannot cash it in without your mother's and grandmother's permission, there is, most likely no gain because thr asset isn't yours. Some assets are not taxable in any case. Government stocks are a good example, although you have to be aware of the bond-washing rules.

Without kowing exactly what sort of asset it is, it is hard for me to give any further specifics. If you do decide to sell, you will need to compute the gain. As a strating point, look at what was paid for it and deduct that from the likely proceeds. If it is less than 8,500 you do not have a liability but may have to report the gain.

Edit: What happened to the previous answer, the one that was based on US tax law?

yes

no but your grandmother and mother will, if they are alive or it comes out of their estate. you still get CPI allowed by tax office
As a trust it sounds like a family trust fund that is taxed as the money goes in at a reduced rate so tou could be up for more tha then you think.
Used moslty for planning retirement