Qurbani is Wajib (obligatory) on every Muslim who is:
• of sound mind – mature (has reached the age of puberty),
• Muqeem (i.e. he is not a Shari traveller)
• Possesses the amount of 612,36 grams of silver or wealth equivalent to that value which is in excess of one’s basic needs and debts, on any of the three days of Qurbani. It is not necessary that this amount be in one’s possession for a complete lunar year.

Note:

1. Qurbani is not incumbent on a child r an insane person whether they own wealth equivalent to the amount above or not, nor is it Wajib upon their guardians to perform it on their behalf.
2. Similarly, it is not Wajib on a Musaafir (one considered a traveller in Shariah). A Shar’i traveller is he who proceeds on a journey with an intention of travelling 77 kilometre`s. He will be treated as a traveller as soon as he leaves his town. However if he intends residing at any place for 15 days or more then he will cease to be a traveller when he arrives at that location.
3.  A person upon whom Qurbani is not necessary should not incur debts beyond one’s capacity to offer the Qurbani.
4.  If Qurbani is not compulsory on a person, for example a Musaafir, then it is virtuous to do so if it is within the person’s means.

No Alternate for Qurbani
Some people think that instead of offering a Qurbani they should give its amount to some poor people as charity. This attitude is totally wrong. Actually, there are different forms of worship obligatory on Muslims. Each one of them has its own importance and none of them can stand for the other. It is not permissible for a Muslim to perform salaah instead of fasting in Ramadaan, nor is it permissible for him to give some charity instead of observing the obligatory Salaah. Similarly, Qurbani is an independent form of worship and this obligation cannot be discharged by spending money in charity.

However, if somebody, out of his ignorance or negligence, could not offer Qurbani on the three prescribed days (10th, 11th and 12th Zul Hijjah) then, in that case only, he can give the price of a Qurbani as Sadaqah to those entitled to receive Zakaat. But during the days of Qurbani no Sadaqah can discharge the obligation.