In the name of Allah the most Beneficent and Merciful.

Reward for the living can be sent and Allah can be invoked that He sends His blessing on the living and the dead. The prophet of Allah (May Allah bless him and grant him peace) performed a Qurbani and asked for all his Ummah (past and present) to be included in the reward.

However, if a person misses their obligatory duties such as Salaah, Fasting in Ramadhan, paying Zakah and perfoming Hajj when they are fit to do so, then no one can compensate for that as these are Fard-e-Ayn, individual obligations. One can only advise them and pray to Allah that they come to the straight path. No voluntary reward is accepted unless the obligatory duties are performed. (Alamgiri)

Of course Allah knows best

[answer provided by: Muhammad Salim Ghisa]