Recovery of tax: administrative modes allow deduction, attachment, third party notice and sale to satisfy unpaid liabilities. Section 72 empowers the proper officer to recover unpaid amounts by deduction from money owing to the debtor, detention and sale of goods, or by issuing a notice to third parties holding or owing money to pay sums sufficient to discharge the liability; the notice binds recipients, may be amended or revoked, and renders third-party payers liable to the Government to the extent they discharge the debtor's obligations after service, subject to a defence that the sums were not due or held for the debtor at service, while payments in compliance discharge the payer to that extent.