You may have received a fine in a situation where you did not intend to commit an offence. For example, stopping in a no stopping area because you didn't see a sign. Most fine matters are 'strict liability'. This means that even if you didn't mean to commit the offence, simply doing it is enough.
If you committed the offence, even unintentionally, you will generally need to plead guilty at court. You can provide an explanation when you plead guilty to explain why you don't think the fine is fair. The court will hear your explanation and consider whether there are any reasons why you shouldn't be fined or why you should get a smaller fine.
For more information, see Pleading guilty.
If you didn't commit the offence, for example, it wasn't you that committed the offence or you have a defence, you may enter a plea of not guilty. Sometimes working out if you have a defence may be difficult.
For more information, see Pleading not guilty.
Some offences are very difficult to challenge in court. If you were caught speeding by a speed camera, the photograph taken of your car will be used as evidence against you. It will include the speed you were going. The photo will be conclusive proof that you were speeding, unless:
the photo shows you weren't the driver
the photo shows a car other than yours
there is no security indicator on the photo.
The security indicator is evidence the photo has not been changed. If the security indicator is not present, the court may not accept the photo as evidence.
Before applying to have your fine heard in court, you should get legal advice.