A tender, to be valid, must satisfy the following essential requirements
(i) It must be unconditional.
(ii) It must be for the whole obligation and must not be in instalments, if the contract requires in full.
(iii) It must be by a person who is in a position and willing to perform the promise.
(iv) It must be at the proper time and place.
(v) It must be in proper form.
(vi) It must be made to a proper person i.e. to the promisee or his authorized agent.
(vii) In case of the tender of goods the promisee must be given a reasonable opportunity to inspect the goods.
(viii) It may be made to one of the several joint promisees.

(i) When its performance becomes impossible.
(ii) When the parties to it agree to substitute a new contract for it or to rescind or alter.
(iii) When the person at whose option it is voidable rescinds it.
(iv) When it is illegal

"When a person has made a promise to two or more persons jointly, then unless there is a contract to the contrary, the right to claim performance rests as between him and them, with them during their joint lives  and after the death of them with representatives of such deceased person jointly with survivors and after the death of last survivor, with the representatives of all jointly".

According to section 45 of Indian Contract Act Devolution means,"When a person has made a promise to two or more persons jointly, then unless there is a contract to the contrary, the right to claim performance rests as between him and them, with them during their joint lives: and after the death of them with representatives of such deceased person jointly with survivors,and after the death of last survivor, with the representatives of all jointly".

There are mainly two ways of performing a contract such as:
i) Actual Performance:
When the party has done what he had undertaken to do,it is called actual performance.In actual performance,the party is to fulfil all his obligations under the contract.
ii) Attempted Performance:
When the party offers to perform his obligation, it is not accepted by the promisee.A valid tender of performance is considered to be the performance of a promise.

(i) According to section 50, where the manner and time for performance are fixed by the promisee, the promise should be performed in the manner and at the time prescribed by the promisee.
(ii) Example (1): T owes S Rs 2,00,000 to accept T's car value of Rs.1,00,000 in reduction of the reduction of the debt. The delivery of the car will amount to a part payment of the debt.
(iii) Example (2): A and B were mutually indebted that A owed Rs 2,00,000 to B and B owed Rs 2,50,000 to A. B paid the difference of Rs 50,000 to A and the account was settled by setting off one debt against another.

Those persons who have made a joint promise, then unless a contrary intention appears in the contract, all such persons, during their joint lives and after the death of the last survivor, representatives of all, jointly must fulfil the promise are called joint promisors.
Benefits:
1. The promises are mutual. So both the parties are benefited.
2. Reciprocal promises maybe independent (or) dependent (or) concurrent. So flexibility will be there.

Only a promisee can demand performance and not a stranger demand performance of the contract.

The promisor himself or his legal representatives or by any other competent person employed by him performs the contract.

A valid tender of performance is considered to be the performance of a promise.