Is money borrowed against expected dues from the company, with the intention of not returning to it after the leave, permissible or forbidden?

If the company were to know your intention, they would refrain from lending to you, and this indicates a trick and betrayal that is not permissible. You can obtain your entitlements through proper means by submitting your resignation and explaining the truth of the matter without trickery or betrayal. The entitlements may increase or decrease according to the contract terms, so follow the correct procedures. Trickery and betrayal are not among the ethics of a believer, except out of necessity to remove injustice. If you have already borrowed, you are permitted to benefit from what you borrowed, and you are obliged to repay it in full if your entitlements are not sufficient, for the Messenger of Allah, peace and blessings be upon him, said: "Whoever takes the money of the people with the intention of repaying it, Allah will repay it on his behalf; and whoever takes it with the intention of wasting it, Allah will waste him." Narrated by Al-Bukhari.