Refund withholding permitted where returns are unfiled or liabilities remain unpaid, and authority may withhold refunds to protect revenue. Refunds may be withheld where a registered person has not filed returns until filing, where tax, interest or penalty remains unpaid and unstayed until payment, and the proper officer may deduct unpaid taxes from refundable amounts; a Commissioner or Board may withhold an ordered refund under appeal if grant would adversely affect revenue.