Before you think about altering any staff contracts, make sure you know exactly what is in the original. Every employee has a contract as soon as they start working for you, even if it has never been written down.
In addition, employees who work for you for a month or more must be given a written statement of main employment particulars within two months of joining. It is not itself a contract, but it can provide evidence of the contract's terms if there is a dispute. Read more on the written statement.
A contract contains both express and implied terms.
Express terms are those which are explicitly agreed between employer and employee, either in writing or orally.
They will be made clear in any letter of appointment or written or oral statement made by the employer and accepted by the employee. Express terms may also be written into an individual contract based on other documents such as collective agreements and company handbooks.
Implied terms are not spelt out in a contract in some cases, because they are considered too obvious to mention. For example, if you offer someone a job, it is implied that they will not steal from the company. Another implied term is that the employer will provide a safe working environment.