Stay of proceedings excludes that period from limitation for tax determination and allows re-determination if fraud not proved. Where a stay on notice or order is in place, the stay period is excluded from computing limitation for tax determination; if fraud or wilful misstatement charges in a fraud-based notice are not established on appeal, the proper officer shall determine tax treating the notice as if issued under the general assessment provision. Orders directed by appellate bodies must be issued within two years of communication. Procedural safeguards require an opportunity to be heard, limited adjournments with reasons, orders stating facts and reasons, and that demands not exceed notice grounds; interest applies on short-paid tax and appellate modification adjusts interest and penalty accordingly.