Official Dispatch No. 1063/CT-TTHT dated February 1, 2018 provides guidance on documents for air ticket expenses purchased via e-commerce websites for employees traveling on business to serve business activities as follows:

In case an enterprise purchases airline tickets via an e-commerce website for employees traveling on business to serve the enterprise's business activities, the document used as a basis for calculating deductible expenses are  electronic airline tickets, boarding passes and non-cash payment documents。In case an enterprise cannot recover the employee's boarding passes, the documents used as a basis for calculating deductible expenses are electronic airline tickets, decisions or documents appointing employees to go on business trips and non-cash payments documents。

Pursuant to the above regulations, in case an enterprise signs a contract with a collaborator to perform work serving the enterprise's business activities, the contract stipulates that the enterprise shall bear the costs of air tickets for the collaborators. Then, the documents used as a basis for calculating deductible expenses are electronic airline tickets, boarding passes and non-cash payment documents.

Thus, in addition to normal documents, when buying air tickets via e-commerce websites, an enterprise that wants to deduct this cost when calculating taxes must have additional non-cash payment documents for this air ticket.