What is the ruling of Islamic law on deducting 8% from one's salary for a "Loyalty and Belonging Fund" which pays 100 months of the last basic salary upon retirement?

It is forbidden to subscribe to investment funds in usurious banks, even if they are commercial and not solidarity-based. One must resign immediately and take only the amount of money that was deducted. If the subscription was compulsory, then upon reaching retirement or death, only the deducted amount should be taken. Any excess is considered ill-gotten gain that must be disposed of by spending it on general Muslim welfare.