What you will see soon on our point of sale software on the credit notes as on the gift vouchers already are expiry dates. (see red arrow above)
Our understanding of the law, and we are not lawyers and not qualified to give legal advice is that this is acceptable as long as the period is reasonable. You should check what is considered reasonable by your undustry body.
The big problem at the moment is that legally a new owner must honour existing gift cards and vouchers if the business was sold as a ‘going concern’. This has resulted in these owners having to pay debts that they were never knew about. In one case, I know about one of the old owner's brother presented a big gift voucher to the new owner. It does not seem fair.