I live in Canada and we can claim income tax refunds on charitable donations. On behalf of my friend who does not live in Canada, nor is a Canadian citizen (and therefore cannot claim for tax refund even if he was present himself in Canada and had made that donation himself), I donated an amount to local Muslim Association and I will be receiving the refund.
My question is, does that refund belong to him or does it belong to me?

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.

If what is meant from the question is that you made a charitable donation to some organizations and then received a tax refund based on that donation, and that you made this donation on behalf of your friend with his money and then got tax refund with the receipt of the donation that you made on behalf of your friend, then if this is the case, the money that you got back as tax refund is not his money. However, what has to be looked at now is the ruling about getting back the money donated as a tax refund. We have already issued Fatwa: 89947 about the ruling on a country taking taxes from the people and the ruling of avoiding such taxes. Therefore, if imposing taxes (by the government) on the people is without right (Islamicly unjustified), there is no harm on you to get back these taxes even by tricking them as it is money taken from its owners without a right, and the owners of this money have a right in getting back their money. Furthermore, it is permissible to get back the money that the government took with right [for instance if it imposed taxes to provide essential services, e.g. education, health care, and other services] if it [the government] allows people to get back the taxes that they paid. So in the above cases it is permissible to get back a tax refund and the money that you get is yours and not your friend's.

As regards getting back the tax rightfully taken by the government with receipts of donations made by others, then if the government allows it, it is permissible to get the refund, but if it does not allow it, then it is not permissible as this is lying and cheating and the money that you get back in this case is not yours.

Allaah Knows best.