According to the official letter No.2327/TCT-CS:
If enterprises conduct promotion activities without notification or registration in writing with Department of Trade and Industry as regulations of Law on commerce, when goods are delivered to customers, enterprises must prepare VAT invoices, declare and pay VAT. The expenses for production or buying goods to conduct the promotion activities are included deductible expenses but not exceed 10% of total deductible expenses or not exceed 15% of total deductible expenses for the first 3 year newly-established enterprises.
