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 salah instead of fasting in Ramadan, nor is it permissible for him to give some charity instead of observing the obligatory Salah. 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, 1lth and 12th Zulhijjah) then, in that case only, he can give the price of a Qurbani as sadaqah to those entitled to receive Zakah. But during the days of Qurbani no Sadaqah can discharge the obligation.
Warning for those who ignore Qurbani
There is a tradition related from Hazrat Abu Hurairah that Rasulullah said that the person who has the means of performing Qurbani but does not do so should not even come NEAR our EIDGAH (place of Eid Namaaz).