Is money earned from undeclared overtime hours, which covers a financial deficit, permissible or impermissible?

It is not permissible for anyone to take government assistance unless the required conditions are met, and it is not permissible to use deception or conceal the true income to obtain it. One must adhere to the conditions of the granting authority and inform them of irregular income. If they deem that it does not prevent one from receiving assistance, then that is acceptable; otherwise, adhering to their stipulated conditions is obligatory.