Set-off and withholding of refunds: tax authorities may set off or withhold refunds pending assessment with required approval. The substituted section permits tax authorities to set off all or part of a due refund against amounts payable by the taxpayer after giving written intimation, and to withhold a refund where assessment or reassessment is pending and the refund is likely to adversely affect revenue, subject to reasons recorded in writing and prior approval of the Principal Commissioner or Commissioner.