In Vietnam, each VAT invoice must/should go along with a proper contract. The tricky part is that there is not obligation to redact a contract accompanying a VAT invoice written in the law except for real estate transaction or labor contracts. But in case of a tax inspection, if a VAT invoice (over 20.000.000 VND) is found without its contract, it may constitute a liability and a penalty shall be given. This applies for invoices for services and for goods. We follow the latest guidelines from tax inspectors and from our on-the-field experience.
If you do not have a contract that could be legally receivable, please contact your corporate secretary or your accountant, they might be able to help you!