Quite out of the blue, I got a letter from a New York company called Litani offering to buy my Aviva shares. They are offering £5.30 a share which, for me, adds up to just under £2,000. They say they will adjust the sterling price into euro and deposit it into my bank: all I have to do is fill out a yellow form. I am very much an accidental shareholder: these are my only shares and I am not quite sure how I ended up with them. I get very modest dividends from them every year, which I declare to Revenue. I am now wondering what to do. But first I am curious as to how they got my name and details? Why is this happening and who is this US company offering the deal? And is it a good deal? It seems really simple and that appeals to me as I genuinely wouldn’t have a clue how to sell them otherwise. And if I do sell them to Litani, do I declare that to Revenue and will it be taxed? BHYou are one of many Irish shareholders in Aviva who have received these letters in recent days. And because, like you, the vast majority of these are accidental shareholders, it is easy to get confused.You, and most others, almost certainly got these shares when Norwich Union demutualised back in 1997, almost 30 years ago – as one of the eligible 150,000-odd Norwich Union customers in Ireland – or inherited them from relatives who did.A couple of years later, Norwich Union merged with rival insurer CGU, which had itself been formed in 1998 through the merger of Commercial Union and General Accident. CGU had only just bought full control of Ireland’s Hibernian Insurance.[ The mortgage is paid off; what can we do with the €800 a month now available to us?Opens in new window ]If you’re of a certain age, all of these now forgotten companies will be familiar to you. Anyway, after a subsequent rebranding, all these businesses are now known as Aviva, which is registered in London where it trades on the London Stock Exchange.So much for the history lesson. The big issue for people who do not regularly keep up with their investments is that they may misunderstand this as an offer for the company which involves buying their shares.It isn’t. More importantly, it is offering you well below the market price for your shares.Litani is based in Delaware and makes its money – or at least some of it – by way of mini-tenders, offering to buy shares in companies from people. On its website, Aviva warns its shareholders that mini-tender offers “typically involve buying shares at a lower price and then selling them on at the full market price, allowing the buyer to make a profit at shareholders’ expense”.And that’s what is happening here. You say Litani is offering to buy your shares at £5.30 but that is almost 24 per cent lower than the £6.94 at which they were trading in London on Friday.That’s not a good deal by any description.How did they get your details? Aviva was forced to hand over details despite appealing to the high court in London to allow it to refuse Litani access to its share register.If you really are interested in selling those shares, you should approach a broker in person or online. Shop around for the best value, but even the most expensive broker will not cost you what the Litani proposal will.If you do ignore the advice and sign up to this deal – or if you otherwise sell the shares through a broker at full market value – you will need to file a return with Revenue.[ My husband and I are about to turn 80 and want to downsize. What are our financing options?Opens in new window ]Assuming you got the shares originally yourself – that is, you did not subsequently inherit them – they were free and therefore any money you receive will be seen as capital gain.You do not have to pay tax on the first €1,270 of any gain but will be charged 33 per cent on any gain above that level.If the shares were inherited, the “base price” is their value at the time you inherited them. Deduct that (plus any costs incurred in selling them) from the sale price to work out any capital gain.Please send your queries to Dominic Coyle, Q&A, The Irish Times, 24-28 Tara Street Dublin 2, or by email to dominic.coyle@irishtimes.com with a contact phone number. This column is a reader service and is not intended to replace professional advice