You do not need to reference when:
- when you are writing about your own ideas (unless you have included them in a previous assignment)
- when the information you are writing about is common knowledge, for example:
Northampton is in the county town of Northamptonshire.
To decide whether a piece of information is common knowledge, ask yourself whether your reader could be familiar with the information without needing to do any research and whether the information is widely available. If the answer to both of these is ‘yes’, the information is probably common knowledge; but it’s better to err on the side of caution and include a reference if you are in any doubt.