Is it permissible to take money along with the accrued interest if the borrower is forced to pay a bribe to complete his transactions, or should only the principal be taken?

The described scenario is a corrupt Mudarabah (profit-sharing partnership) because the share of each party in the profit is not specified. Consequently, all the profit belongs to the capital provider (the owner of the money), and the worker is entitled to a fair wage for his labor. As for paying a bribe to complete paperwork and obtain one's right, it is permissible in Islamic law if one is compelled to do so, and the sin falls upon the one who forced him to pay. The owner of the capital is permitted to take his money along with any accrued profit, and he must pay the worker a fair wage.