, my name is ***** ***** it is my pleasure to assist you with your question today. The cheque can still be valid as cheques remain valid until the debt is owed to an individual. So if you are still legally owed the money then the cheque can still be valid. However, you may find that the bank refuses to cash it as it is so old and that is done in order to protect the person who issued it, in case payment has already been made via other means or the debt settled.
Also if this firm no longer exists it is likely that they no longer hold the bank account from which the cheque was issued so it would be impossible to make the payment anyway.
It does not mean that the debt no longer exists and the money may still be legally owed to you but the difficulty now would be to find the persons who issued it and force them to pay you.
Whilst you could try and trace the partners behind the firm by calling the Law Society or the Solicitors' Regulatory Authority, even if you find the individuals responsible the business, you would be way too late to actually take any legal action against them because you usually only have 6 years from the time a debt becomes due to pursue it. As this was such a long time ago you would be time barred from pursuing a claim now and if you cannot get someone to voluntarily pay you, then you will be unable to force them to
you are welcome