According to tax law, the use of illegal invoices or documents refers to the use of:

• Fake invoices or documents
• Invoices or documents that are not yet valid or have expired
• Invoices that are suspended from use during a period of forced suspension of invoice use, except in cases permitted by the tax authority
• Electronic invoices not registered for use with the tax authority
• Electronic invoices without a tax authority code in cases where electronic invoices with a tax authority code are used
• Invoices for purchasing goods or services with an invoice date after the date on which the tax authority determines that the seller is no longer operating at the business address registered with the competent state agency
• Invoices or documents for purchasing goods or services with an invoice date before the date on which it is determined that the issuer of the invoice or documents is no longer operating at the business address registered with the competent state agency, or when there has been no notification from the tax authority that the issuer of the invoice or documents is no longer operating at the business address registered with the competent authority, but the tax authority, police, or other competent agencies have concluded that such invoice or documents is illegal.

The illegal use of invoices or documents refers to the use of:

• Invoices or documents that do not fully record the required content
• Erased or incorrectly corrected invoices;
• Forged invoices or documents (invoices or documents that have recorded economic business indicators and content but the purchase or sale of goods or services is wholly or partially fictitious)
• Invoices that do not reflect the actual value incurred or the issuance of forged invoices
• Invoices with discrepancies in the value of goods or services or deviations from the required criteria between invoice copies
• Invoices for circulation in the distribution process or invoices for one type of goods or services used to prove another type of goods or services
• Invoices or documents of other organizations or individuals (except for invoices of the tax authority and cases authorized to issue invoices) to legitimize purchased goods or services or sold goods or services
• Invoices or documents that have been concluded by the tax authority, police, or other competent agencies as being used illegally.

The issuance and use of invoices affect the tax obligations of taxpayers as well as state budget revenues and expenditures. Therefore, taxpayers need to strictly comply with tax policies and laws in general and regulations on invoices in particular when using invoices and certificates in production and business activities to fulfill their tax obligations to the State budget and enjoy benefits such as being commended for enhancing their reputation and achieving business advantages, thereby accompanying the tax sector in development.