When I left school in 1996, I was given a small sheet of paper no bigger than a drinks coaster that listed my exam grades (which weren't anything to boast about).
That piece of paper has long since been lost or destroyed, although I had kept other more formal A4 sized certificates I have gained over the years.
I believe in honesty & integrity when you are completing job application forms - I always declare my correct G.C.S.E. grades. However, because it is 25 years since I left school and I have no tangable record of my results to refer to, I have to go off memory and I have probably made the error myself in saying I got a 'C' when it was in fact a 'D'.
If worst came to the worst and it did later come to light, that you had put an incorrect grade on your application form, you can easily argue it was an honest mistake which many of us can make if you left school X number of years ago.
There's a difference though between making a mistake with what one of your G.C.S.E. grades were, to blatantly lying on the application form and saying you have got eight A* grades when you know you only got D and E grades.
Many prospective employers don't check G.C.S.E. qualifications. My old high school closed in 2001 and was subsequently demolished, so the employer cannot even contact the school.
I am assuming that my G.C.S.E. results will be kept on record by the Education Authority in some dark storeroom somewhere, but I haven't the foggiest knowledge of where you or employers can check historic school examination results.
From my own experience of job hunting - employers very rarely check G.C.S.E. results. If you are applying for a specialist post where you need a specific qualification, then you need to be 100% honest as they will probably want evidence of this prior to offering any contract of employment.
CJ