If you want to extend the employment contract for an indefinite period, continue the actual employment relationship with the employee after the end date of the contract: provide work space, pay wages, - all as usual. In this case, it is not required to enter into any special agreements. In accordance with article 58 of the Labour contract of the Russian Federation (TC RF), the condition of urgency of the contract will automatically lose its validity, the remainder of the document will remain in effect.
If you want to extend the employment contract for a fixed term, do it before the date of expiry of the contract. In accordance with article 72 of the labour code, the employer and the employee may be agreement to change the terms of the employment contract in written form. In the text of this document should contain a provision stating that the parties agreed to present the relevant paragraph of the employment contract as amended. In fact will only change the end date of the employment contract. It is important to bear in mind that, according to the General rule of article 58 of the labour code, the duration of the employment relationship fixed-term agreement shall not exceed five years, even after its extension, if another term is not established by law.
If the date of termination of the contract - not only the change, rework the text of the labour contract completely and make all corrections. Thus, the employer and the employee will be required to sign two documents: an agreement modifying the terms of the employment agreement and the employment agreement as amended.
Note that it is unacceptable extension of fixed-term employment contract to mask the possibility of concluding with an employee an indefinite contract. In accordance with article 58 of the labour code, if it is established that an employment contract for a definite period have been concluded without sufficient grounds, solely for the purpose of evasion from granting to the worker of guarantees and rights, which implies a permanent contract, the court finds such a contract concluded for an indefinite period.
Sometimes fixed-term employment contract cannot be extended, for example if it is made to replace a temporarily absent employee, for performance of seasonal works in some other cases.