Should an amount of money of unknown origin, which was spent 12 years ago, be put into charitable work with the intention of reward on behalf of its owner to clear one's conscience?

If money is transferred to your account, and it was by mistake, it is obligatory to return it to its owner. If you are unable to identify the owner, you should give it as charity on their behalf, informing them later to give them the choice between confirming the charity or taking the money. However, if it was intentional, which is a remote possibility, you are permitted to keep it. Sheikh al-Islam Ibn Taymiyyah mentioned that if someone possesses money whose owner is unknown, such as a repentant usurper, a betrayer, or one who deals in usury, they should spend it on those in need and for the benefit of Muslims. This also applies to any money whose owner is unknown, whether it be from usurped items, loans, deposits, or money taken from thieves.