Contracts of indefinite duration almost always include a clause allowing for termination "for convenience" or "without cause", as do many other forms of contract; otherwise, there is a risk that the parties will be bound to perform their obligations under the contract indefinitely, with no way out other than through breach. A typical clause might read:
"Either party may terminate this Agreement by giving to the other party at least 30 days' written notice of termination."
This letter template can be used for the giving of a notice under this type of termination clause. In order to use the template, you should first make reference to the relevant termination clause. You should then calculate the consequent date and time of termination - if there is any uncertainty in this regard, take a conservative approach.
You should ensure that the notice and the procedure you use to serve the notice on the other party comply with any express requirements relating to contractual notices in the contract. Even if there are no such requirements, it is best to use a form of service that creates evidence of the fact of service (eg a courier delivery note).
You should review the entire contract to ensure that you are aware of all provisions which may have an impact upon termination. For instance, you will also need to consider what post-termination obligations might apply. Typical post-termination obligations might cover the return of confidential information and the payment of outstanding amounts.
Contract clauses providing for termination for convenience (or without cause) can be distinguished from other common types of termination clause: termination upon breach; termination upon bankruptcy or insolvency; termination upon change of control, etc. This letter should not be used in relation to termination under these other types of termination clause.
If you are in any way uncertain about your legal position in relation to the termination of a contract, you should take professional advice.