A contract of employment may be oral, written, implied or a mixture of all three. If you have no written contract your continued attendance at work and your employer's habit of paying you wages form the substantive part of the contract. The description of your job is not strictly speaking part of the Contract Of Employment. If you have not been given a written Job Description you can deduce the terms of your job from a variety of places including:
* the original job adverts
* letters of application and acceptance
* agreements concerning duties and pay rates (written or oral)
* staff rules and handbook
An oral contract is as binding as a written one, although its terms may be more difficult to prove.
Where an employee has been working for an employer for a month or longer, they should be given a statement (written or oral) of the terms and conditions of the job, and certainly within two months of starting their employment. In effect this is usually presented orally at the interview, and amended orally from time to time. As a courtesy if the Job Description was originally verbal then its alteration need only be verbal. Written Job Descriptions are usually changed by another written Description. There is no legal requirement for this convention, however.
This Job Description, written or otherwise, does not constitute a contract, but in the case of a dispute it can be used as evidence of an employee's terms and conditions.
If your employer says that from a certain time your job will include new tasks, additional to your present ones, and you carry on without comment then you have implied your agreement with the new arrangement. Had you said that the additional work would attract more wages or time off in lieu or some other arrangement when your employer told you of the change then you would have entered a negotiation phase and you would be quite entitled to