You only have a clear right to a bonus if it is specified in your contract of employment. In such situations it may only apply if you attain specified targets, e.g. sell a certain number of products or increase your productivity by a certain amount.
However, if it has become custom and practice to pay one - in other words if you have had one every year so far - you may be able to argue that it has become an unwritten part of your contract, and claim that an unlawful deduction has been made from your wages.
Just One More Click: Doggy drama about staying safe online at work.