Although a cheque is normally regarded as 'stale' by a bank 6 months after issuance, legally it is valid any time until presentation, as per Section 74 of the Bills of Exchange Act 1882.
"Presentment of cheque for payment.
Subject to the provisions of this Act—
(1)Where a cheque is not presented for payment within a reasonable time of its issue, and the drawer or the person on whose account it is drawn had the right at the time of such presentment as between him and the banker to have the cheque paid and suffers actual damage through the delay, he is discharged to the extent of such damage, that is to say, to the extent to which such drawer or person is a creditor of such banker to a larger amount than he would have been had such cheque been paid.
(2)In determining what is a reasonable time regard shall be had to the nature of the instrument, the usage of trade and of bankers, and the facts of the particular case.
(3)The holder of such cheque as to which such drawer or person is discharged shall be a creditor, in lieu of such drawer or person, of such banker to the extent of such discharge, and entitled to recover the amount from him."
When I used to audit the clearing process 30 odd years ago, cheques over 6 months old would be marked 'Refer to Drawer, Please Represent', giving time for the cheque to be re-dated or cancelled and replaced. I must admit that I do not know what happens nowadays regarding manual cheque clearing.