Arm's length price rules set prescribed methods for related-party transactions and allow tax authorities to determine prices if records unreliable. Computation of the arm's length price requires selecting the most appropriate method from prescribed comparability approaches, with the assessing officer empowered to determine the arm's length price during assessment if transaction pricing, documentation, or data reliability is deficient; the assessee must be given an opportunity to show cause and the officer may recompute total income accordingly, with prescribed limits on deductions where income is enhanced and rules preventing recomputation of the other associated enterprise's income in certain circumstances.