Your contract of employment should contain a clear written term specifying your rate of pay and other pay elements, which are a matter of agreement between you and your employer.
The written statement of employment particulars, which employees must be given within two months of starting work, must tell you your rate of pay, and when you will be paid (i.e. weekly, monthly, etc.).
You have some important rights relating to your pay, including the right not to be paid less because of your gender (the right to equal pay), or because of your race or ethnicity, or because you work part-time, or as a temporary (fixed-term) employee. Agency workers who have worked for 12 weeks in the role with the same hirer also have important pay equality rights.