What Happens If You Do Not Offer Ud-hiyah for Years?
Question

Muslim female who has been earning since a few years but recently came to know that Qurbani is wajib on her because she is earning. How can she compensate for all those previous years for which she did not offer sacrifice.
Praise be to Allah.Is Ud-hiyah obligatory?
The scholars (may Allah have mercy on him) differed with regard to the ruling on Ud-hiyah : is it obligatory or Sunnah Mu’akkadah (a confirmed Sunnah)? The correct view is that Ud-hiyah is Sunnah Mu’akkadah for the one who can afford it, but there is no sin on the one who does not do it. 
What happens if you do not offer Ud-hiyah for years? 
If a person does not offer Ud-hiyah although he can afford to do so, he is missing out on a lot of reward that results from offering the sacrifice, but he is not sinning, and he does not have to make up for what he missed in years past, because Ud-hiyah is Sunnah and the time for it has gone. This is the case if he did not make a vow to offer a sacrifice, in which case it is obligatory for him to fulfil his vow and offer Ud-hiyah . 
It says in Al-Mawsu`ah Al-Fiqhiyyah (34/46): “If a person does not offer a sacrifice before the time has passed, if it was a voluntary sacrifice he should not offer it; rather he has missed the opportunity to offer a sacrifice this year. But if it was a vow, he has to offer a sacrifice and make up for what he was obliged to do.” 
Based on that, if she wants to offer Ud-hiyah , then from now onwards she has to prepare ahead of time, so that when the next `Eid Al-Adh-ha comes, in sha Allah, she will have prepared her sacrifice beforehand, so she will not have missed the time for Ud-hiyah , as happened in the past. 
We ask Allah to help us and you to do that which He loves and which pleases Him, and to accept righteous deeds from us and from you. 
And Allah knows best.