Settlement of tax cases requires full disclosure and prior payment of tax and interest before filing, with related party rules. Section 245C authorises applications to the Settlement Commission contingent on a prescribed full and true disclosure of undisclosed income, payment of the tax and interest that would have been payable if that income had been declared earlier, and payment of prescribed fees; applications cannot be withdrawn and require intimation to the Assessing Officer. The section defines related-person and substantial-interest rules affecting eligibility and prescribes year-wise methods for calculating the additional tax attributable to disclosed income, with aggregate computation where multiple years are disclosed.