Appeal filing limits preserve tax authorities' ability to bring later appeals on identical issues despite earlier non-filing. Section 373 empowers the Board to prescribe monetary thresholds and directions regulating the filing of appeals by income-tax authorities. Non-filing pursuant to those directions does not preclude the authority from later appealing the same issue in other years or against other assessees, nor does it permit an assessee to claim that the authority has acquiesced; tribunals must have regard to the Board's directions and the circumstances of filing or non-filing.