You can obtain an NHS voucher from your optician when you have a sight test.
Enter the details into the website exactly as they are on your GOS3 form and bring the original NHS form to your fitting appointment. This will reduce the amount that you are charged through the website accordingly. If your details have been entered incorrectly, the amount you may be charged could be affected. If you do not bring the form in to the store, you will be charged the full amount for your glasses.