Overtime refers to any minutes or hours an employee works beyond their contracted or scheduled hours. Both salaried employees and staff paid by the hour can work overtime, though there are legal limits on the number of hours an employee can work per week.
If an employee works more than their contracted or scheduled hours, then they are considered to be working overtime and may be entitled to extra pay.
Under UK law, employers do not have to pay overtime to part-time staff until they've worked the same number of hours as a full-time employee (unless their contract stipulates otherwise).
It’s important for employers to keep accurate records of the hours their staff work. Staff rotas can be useful for this, but timesheets are usually a more accurate way to record the hours your staff have actually worked on a given day.