What is the ruling on working as an accountant in an organization whose board of directors manipulates accounts and refuses to examine them, and is it obligatory to leave the job when other employees are aware of this and condone it?

What can be done depends on two things: the degree of certainty the questioner has about the existence of administrative corruption or the unlawful appropriation of funds, and the legal situation in the country. If he is certain of the corruption and can prove it, then he should refer the matter to the competent authorities if he is able to do so and will not incur significant harm, especially after discussing it with the administration. If he is unable to refer it to the competent authorities, then he should ensure the organization's accounts are well-managed to prevent future corruption. He is not obligated to leave his job unless he is forced to participate in the corruption or cover it up.