A Hóa đơn GTGT is only valid if the required information is there and the invoice is signed. Invoi fills most of this from your company profile and the customer record.
#Language and currency
- The invoice must be in Vietnamese. English can sit next to it, usually in brackets — Invoi does this on bilingual templates.
- Amounts must be in VND. If you also show USD or EUR, convert to VND on the same invoice. The VND total is the one that counts.
#Seller (your company)
- Legal name
- Address
- MST (tax number)
- Digital signature (chữ ký số) with a timestamp
These come from Settings → Company profile. Invoi signs in the browser and stamps the time — you do not add the timestamp by hand.
#Buyer (your customer)
When the buyer is a company:
- Legal name
- Address
- MST
Invoi can look these up from the MST so you do not type them by hand. See Customers.
When the buyer is an individual:
- Full name
- Address
- CCCD or passport number
If the buyer does not ask for an invoice, name, address, and tax ID may be left blank under the current rules. Invoi has a system buyer for that case.
#On the invoice itself
- Name of the invoice — for example *HÓA ĐƠN GIÁ TRỊ GIA TĂNG* / *VAT INVOICE*
- Invoice series (ký hiệu) and number
- Issue date
- Line items: description, unit, quantity, unit price, amount
- VAT rate and VAT amount (or the correct no-VAT treatment)
- Total payable
- Total amount in words (số tiền bằng chữ)
- Currency in VND (foreign currency only as a converted extra)
After the tax authority accepts the invoice, it also gets a CQT code. That code is not something you type — it comes back after processing.
#Adjustment and replacement notes
An adjustment or replacement is not valid without a note that points back to the original invoice:
- that this invoice adjusts or replaces another
- original number
- original series (ký hiệu)
- original issue date
Invoi writes this note for you, for example: *Điều chỉnh cho hóa đơn [ký hiệu], [số], [ngày]* or *Thay thế cho hóa đơn [ký hiệu], [số], [ngày]*.
#Optional, but useful
- Payment terms and bank details
- Order / contract number
- Discount — per line or on the total
- Extra notes for the customer (on top of the required adjust/replace note)
#Check before you sign
Wrong MST, wrong buyer name, a missing CCCD on an individual, or a missing VAT rate is what usually forces an adjustment or replacement. Look the customer up from MST (or enter CCCD / passport), then sign.