Chewing tobacco packing machines: duty calculated pro rata on permanent factory cessation; adjustments, refunds, and payment deadlines apply. When a manufacturer permanently ceases work for all machines and files an intimation surrendering registration with the jurisdictional Deputy Commissioner or Assistant Commissioner of Central Excise (copy to the Superintendent), duty for that month is calculated pro rata based on days in the month up to receipt of the intimation; duty paid under the monthly rule is adjusted, excess refunded by the 20th day of the following month and any deficiency payable by the 6th day. 'Ceases to work' excludes stoppages of one or two shifts.