All information provided to us needs to be accurate so that you are properly insured. Most websites will allow you to enter the exact date you got your licence, so it’s always best to do that. However, some will only ask for the amount of years you’ve held your licence.
If you have held your licence for 3 years 10 months, you’ll need to put this down as 3 years, even though it’s closer to 4. Only full years count.