Withholding refunds when reassessment is pending to protect revenue and permit adjustment against resultant tax demand. When assessment is set aside but re assessment is pending, issuing a refund of excess tax may prejudice revenue because additions may be restored; the Income tax Officer should consider withholding the refund by referring to the Commissioner for approval under section 241, and, if withheld, re assessment should be completed promptly so the refund can be adjusted against resultant tax demand and avoid interest.