Duplicate invoices are one of the most common accounting errors, especially in businesses with multiple branches or using multiple accounting systems – eInvoice – in parallel. While not a complex operational error, failure to detect and address it promptly can lead to the loss of VAT deduction rights, incorrect recording of revenue and expenses, and even penalties under Decree 125/2020/ND-CP.
The important thing is: How to handle duplicate invoices It must comply with regulations, have complete supporting documents, and a clear distinction must be made between different levels of errors in order to choose the appropriate option for cancellation, correction, or supplementary declaration.
This article will guide you through the entire process from A to Z: identifying duplicate invoices, the causes of errors, how to handle each case, how to declare correctly according to the law, and technology to help prevent duplication automatically (Bizzi AI). All of this is based on the latest regulations and practical experience for thousands of businesses in Vietnam.
1. What are duplicate invoices and why do businesses need to handle them promptly?
When it comes to How to handle duplicate invoicesThe first thing businesses need to understand is that this error is not just a "minor accounting mistake." Duplicate invoices, if not detected and handled promptly, can lead to the risk of losing tax deductions, inaccurate financial reporting, and unnecessary penalties. Therefore, the most important step is to correctly understand the definition and legal status of duplicate invoices in order to have an accurate handling plan.
1.1. Clear definition as prescribed
According to Decree 123/2020/ND-CP, each transaction for the sale of goods or provision of services may only be recorded as such. a single invoiceThis means that any instance of issuing two or more invoices with identical content will be considered a duplicate, whether accidental or due to a system error.
In fact, duplicate invoices This occurs when multiple invoices with the same information regarding the seller, buyer, goods, payment value, tax rate, or issuance date are issued for the same transaction. This is a common error in businesses with multi-step or multi-person operational processes, but according to legal regulations, duplicate invoices are always considered a violation. invalid and must be handled according to specific procedures.
1.2. Legal implications and consequences of failure to address the issue.
From a legal perspective, duplicate invoices are not considered valid documents. The direct consequence is that businesses... Input VAT is not deductible.These expenses are not recognized as reasonable expenses when settling corporate income tax, and may be disallowed during tax audits and inspections.
If not done How to handle duplicate invoices In accordance with regulations, accountants or businesses may be subject to administrative penalties. 2–8 million VND According to Decree 125/2020/ND-CP, depending on the severity of the error and its impact. In serious cases, if the tax authorities assess this as an offense. issuing fake invoices If a business misreports its revenue and expenses, it may face in-depth inspections, leading to numerous legal risks and compliance costs.
1.3. Practical Insight
In a real-world operating environment, duplicate invoices usually don't originate from incorrect transactions but rather from other sources. System errors, process failures, or coordination issues between departments.In businesses with multiple branches, data synchronization between eInvoice, ERP, and accounting software systems is often not seamless. Even a weak network connection or a lack of a proper system mechanism can cause problems. Idempotency transaction verificationAccountants may inadvertently send invoices to the system multiple times.
This makes duplicate invoice errors a "potential risk" that many businesses only discover during reconciliation or when tax authorities request an explanation. Therefore, understanding the process and supporting technologies is crucial. How to handle duplicate invoices This not only helps fix errors quickly but also helps prevent them from the root.
2. Identifying signs and causes of duplicate invoices
Before applying any How to handle duplicate invoices Therefore, businesses need to be aware of the early warning signs. The earlier the errors are detected, the lower the cost of correction, avoiding the risk of misrecording revenue, losing VAT deductions, or being required to explain by the tax authorities. Simultaneously, understanding the root cause helps businesses adjust processes or system configurations to avoid duplication in the future.
2.1. Early warning signs
Duplicate invoices usually have relatively clear identifying signs if accountants carefully check them from the issuance or data reconciliation stage. The most common sign is that two invoices have... Same invoice number, same symbol, and same issue date. — which almost certainly indicates that the invoice was issued twice for a single transaction.
Additionally, some businesses discover duplicate invoices when they see them. Two invoices have the same customer, the same value, and the same product, but different tax authority codes., especially when using invoices with tax authority codes. Another fairly typical case is when the reporting system... "Send failed error"The accountant clicked "resend," but in reality, the submission request had already been received and a code assigned; as a result, two different versions of the invoice were issued.
When searching on the General Department of Taxation's portal, the system often returns messages such as: "The invoice already exists.", "Duplicate code has been issued"Or displaying multiple identical invoices. These are all warning signs that need to be checked immediately to avoid risks related to declaration and accounting.
2.2. Common Causes
Duplicate invoices can stem from a variety of causes, ranging from technical to operational. Below are the main causes observed in many businesses, along with specific analyses:
| Error group | Detailed description | Rate of occurrence |
| Technical error | Network connection interruptions caused the system to resend requests for codes, resulting in invoices being assigned codes twice; there is also a lack of idempotency mechanisms to prevent duplicate orders. | 35% |
| User operation error | The accountant forgot to issue an invoice, had to re-enter the data, and issued a new invoice; or was working on multiple tabs or systems simultaneously. | 40% |
| ERP – eInvoice synchronization error | Slow synchronization or running two processes in parallel causes the system to issue two invoices for the same transaction. | 15% |
| Tax connection API error | The tax authority's system is undergoing upgrades or experiencing congestion; the order to issue a code is being duplicated even though the system displays an error status. | 10% |
3. How to quickly and accurately detect duplicate invoices with evidence.
To make the right choice How to handle duplicate invoicesBusinesses need to understand methods for early detection and have clear evidence for internal reconciliation or dealings with tax authorities. Below are three levels of inspection – from manual to automated – that help accounting teams detect issues with near-perfect accuracy.
3.1. Check the invoice code
This is a basic but crucial verification step that helps accountants detect duplicates in minutes.
How to check for proper standards:
- Compare Some bills, Sample symbols, Invoice symbol, Release date, Tax authority code.
- If all the same elements → almost 99% is a duplicate invoice. and the processing procedure needs to be activated immediately.
- Access Information portal Electronic bill of the General Department of Taxation (hoadondientu.gdt.gov.vn) → enter lookup code → view statusCode granted”, “Cancelled" or "It already existed.".
Why is this step important? Because the code issued by the tax authority is unique, if the system returns a duplicate, you have sufficient evidence to request the seller to adjust or cancel the invoice.
3.2. Data reconciliation between accounting software and eInvoice
This is a more accurate detection method, helping to eliminate errors caused by manual operation or data synchronization.
Effectiveness testing process:
- Using the feature "Match the list of invoices" on accounting software.
- The system will scan the following fields: MST, amount of money, release date, supplier name → If it's a duplicate → Automatically flag it.suspected infection".
- Continue comparing 3D including:
- PO (Purchase Order)
- GR (Goods Receipt)
- Invoice
→ This helps eliminate the possibility of "recording the same transaction twice".
Benefit: Reduce the risk of late detection by 70–80%, especially in businesses with multiple branches or multiple data sources.
3.3. Automatic detection using AI
This is an advanced detection level, suitable for businesses that want to closely monitor and minimize human error.
Bizzi AI use more 20 criteria for identifying duplicate invoices, include:
- Parasite 100% amount, But different invoice symbols.
- Parasite Supplier's Tax ID and release date, although the content is slightly different.
- Matching product/service descriptions is determined by an algorithm. Fuzzy Matching, even if the seller intentionally changes the description.
- In the case of an invoice lacking a lookup code but with matching content, use code 80–90%.
How it works:
- The system continuously scans for new invoices.
- Flag immediately if a suspected case is detected.
- Block the accounting entry and require the accountant to verify it before proceeding with the process.
- Display a warning on the dashboard with evidence: invoice code – time – matching point that is duplicated.
Why is AI useful? For businesses that generate hundreds or thousands of invoices per month, AI helps save time, avoid tax penalties, and ensure internal compliance.
4. Handling duplicate outgoing invoices – detailed instructions for each situation.
When a business discovers duplicate outgoing invoices, it must absolutely... Do not delete manually. or changing data on the system. The processing must be based on status marker Regarding invoices: whether they have been sent or not, and whether taxes have been declared or not. Below is a complete and easy-to-apply guide for all businesses when implementing this. How to handle duplicate invoices in accordance with the law.
4.1. Case 1: Duplicate invoices but not yet sent to the buyer
- Cancel directly through the electronic invoicing software.
- Clearly state the reason as "Duplicate – not yet released to the buyer".
- No notification to the tax authorities is required.
- Maintain electronic records and internal minutes for future review.
4.2. Case 2: Invoices have been sent but taxes have not yet been declared.
- Set up Minutes of electronic invoice recall (Digital signatures from both parties).
- Cancellation notification on the eInvoice system as follows Form 04/SS-HĐĐT.
- Create a correct invoice, issue a new code, and send it to the buyer.
4.3. Case 3: Duplicate invoices already declared
- Do not delete or cancel the software without permission.
- Perform invoice adjustment reduction, not to be recorded.
- Simultaneously, Adjustment declaration for the next period in VAT tax return, item [38].
- Notify the tax authorities using Form 04/SS-HĐĐT along with an explanation.
⚖️ Legal basis:
Businesses can compare the following documents after processing duplicate invoices:
- Articles 19 and 27 of Decree 123/2020/ND-CP (Regulations on cancellation, recall, and adjustment of electronic invoices).
- Circular 78/2021/TT-BTC – Article 7 (Instructions on handling invoices with errors).
- Official Document No. 2257/TCT-CS of 2023 of the General Department of Taxation on guidance for handling duplicate electronic invoices.
5. Handling duplicate input invoice declarations – avoiding loss of VAT deduction rights.
Duplicate input invoices are a common error in businesses with multiple branches, numerous data entry personnel, or lax document control processes. If not addressed promptly, businesses may have expenses disallowed, face VAT arrears, and even be accused of intentional misdeclaration. Below is a detailed guide to each case. How to handle duplicate invoices In accordance with tax authority standards.
5.1. When discovered during the current filing period
If you discover duplicate invoices within the same tax-filing month/quarter, the process is relatively simple and low-risk.
The correct way to do it:
- Resubmit the VAT tax return for that period with the corrected data (replacing the old return).
- Update the internal accounting journal, clearly noting the rejected invoices to avoid them being re-entered in the next period.
- Keep records proving you corrected the error in a timely manner (system logs, internal emails, etc.).
Benefit: Processing the issue within the same period helps avoid the risk of losing VAT deduction rights and prevents penalties for incorrect declarations.
5.2. When discovered after the declaration period (supplementary - adjustment)
This is the most common case: invoices are duplicated from 1-2 previous periods. In this situation, businesses need to identify the issue. Does the error change the amount of tax payable or the amount of tax deductible?.
Case 1 – No impact on tax amount:
If the duplication does not change the amount of VAT deductible or VAT payable, the business only needs to:
- Send amended declaration for the relevant period.
- No complicated additional documentation is required.
Case 2 – Affects the tax amount:
If the amount of tax payable or the amount of tax deductible changes, full documentation must be prepared.
- Submit Supplementary Declaration Form 01/KHBS.
- Attached Explanation for supplementary declaration – Form 01-3/KHBS To clarify the reasons for duplicate declarations.
- Note: Documents must be submitted. before the tax authorities announce the inspection/audit decision. to avoid being accused of providing false information.
Tips to reduce risk: Businesses should use an automated invoice duplication checker system like Bizzi to reduce data entry errors before submitting tax returns.
5.3. When the tax authorities have inspected and discovered
If a business doesn't detect the issue itself and instead relies on tax authorities for inspection, the process is simpler but carries higher risks.
Procedure:
- Once the tax authorities have issued it Decision on handlingBusinesses only need to file an amended declaration in the same period in which they receive the decision.
- It is not permitted to go back and adjust previous records.
- Businesses must accept this. Penalties are imposed according to Decree 125/2020/ND-CP.The penalty depends on the offense: false declaration, tax evasion, tax shortfall, or inflated VAT claims.
Advice:
This is a situation no business wants to encounter. The process How to handle duplicate invoices The best approach is still early detection using technology and pre-declaration control.
6. Instructions for preparing and submitting Notification 04/SS-HĐĐT on the Invoice Portal
When electronic invoices are discovered duplication or errors, businesses need to establish Announcement 04/SS-HĐĐT To notify the tax authorities and cancel the invoice in accordance with regulations, follow these steps:
Step 1: Log in to the Electronic Invoice Portal
Access the following address: https://hoadondientu.gdt.gov.vn and log in using your registered business account.
Step 2: Select Notification Template 04/SS-HĐĐT
- Go to the menu: "Notification that the electronic invoice contains errors"
- Select Form 04/SS-HĐĐT to create a cancellation notice for the invoice.
Step 3: Fill in the information for the invoice to be canceled.
- Some bills
- Invoice symbol
- Verification code (if applicable)
Note: The information must accurately match the issued electronic invoice.
Step 4: Record the reason for cancellation.
- In the section Reason for the error, select or specify: "Duplication"
- This is a common reason why an invoice has been issued multiple times.
Step 5: Send notifications and monitor status
- Press Send so that the tax authorities can receive the notification.
- The system returns one of the following states:
- Received
- Cancellation accepted
- Then, check again. list of invoices to ensure the state "Cancelled" has been updated.
7. Special cases: duplicate errors due to refunds, branches, or API
In reality, duplicate invoices are not only caused by data entry errors, but also stem from more complex situations:
| Situation | The correct way to handle it according to regulations. | Tip |
| Customers can return or exchange goods. | Set up invoice for value adjustment or cancel the original invoice → issue a new invoice that accurately reflects the actual situation. | Bizzi Invoice automatically suggests an adjustment invoice, directly linking it to the original invoice. |
| Branch and headquarters jointly invoice for the same order. | Identify authorized publisherThe remaining invoice will be canceled according to Form 04/SS-HĐĐT. | Audit logs record the issuing entity, preventing internal disputes. |
| API error or invoice resending due to network issue. | Check transaction logKeep the first copy with a valid code; cancel the retry copy that was assigned a code later. | The system automatically assigns a "master invoice" and automatically blocks duplicate copies. |
Tip: Implementing audit logs and automatically marking duplicate invoices helps businesses. Avoid the risk of accidental cancellation or incorrect declaration..
8. The impact of duplicate invoices on tax reporting and accounting.
Duplicate invoices directly impact both sellers and buyers, as well as legal compliance:
- For the seller:
- Recording revenue twice leads to increased corporate income tax.
- An adjusting entry is needed to reduce revenue and output tax.
- For buyers:
- If there is duplicate declaration → input VAT cannot be deducted.
- The deductible VAT and corresponding expenses need to be adjusted downwards.
- Administrative penalties:
- Punish 2–4 million If duplicate entries are created but not yet declared.
- Punish 5–8 million If duplicate declarations are made, it will lead to errors in tax calculations.
- If serious damage is caused, tax recovery and inspection may be required.
9. Preventing duplicate invoices through processes and technology.
To reduce the risk of duplicate invoices, businesses should combine strict internal procedures and automatic technology.
9.1. Establishing internal control procedures
- Clearly define roles and responsibilities: who creates, who approves, and who sends the invoice.
- Maintain audit logs for all operations.
- Set a rule to automatically lock entries when the Tax Identification Number (MST) + Number + Date + Value already exists.
9.2. Establishing periodic reconciliation
- Comparing Invoice ↔ ERP ↔ accounting software every day.
- Use batch checking for duplicates based on custom criteria.
- Report Duplicate Invoice Rate (%) Monthly for the CFO.
9.3. Using software to automatically detect duplicates
- Bizzi AI Fuzzy matching detects duplicate content of different numbers.
- Automatically block payments if a suspected duplicate invoice has not been verified.
- Real-time alerts via email or admin dashboard.
10. Bizzi – An automated solution for controlling and processing duplicate invoices.
Duplicate invoices not only cause problems It requires manpower and is costly., but also potentially tax and audit risksBizzi provides a comprehensive set of tools to help businesses. Detecting, handling, and preventing duplicate invoices. automatically and transparently.
10.1. Bizzi IPA (Invoice Processing Automation)
Bizzi IPA uses RPA + AI To automatically read, extract, and match input invoice information:
- Compare invoice data ↔ PO ↔ GR: Automatically check purchase order number, warehouse receipt number, value, date, VAT, and supplier tax code.
- Detecting duplicate, incorrect, or forged invoices: Include:
- Invoice with duplicate content
- The invoice has an invalid tax identification number (MST) or value.
- Fake invoices or invoices that have not been assigned a code.
- Audit trails are automated records of detection processes, timelines, and personnel involved, which are used for tax audits and inspections.
Tip: Thanks to AI, Bizzi IPA can detect The invoice was suspected of being a duplicate right from the data entry stage.This reduces errors before the invoice is recorded in the ledger.
10.2. Bizzi Expense + EPM Integration
When you discover or suspect a duplicate invoice:
- Automatically "Freeze" spending transactions: Prevent payment until verification.
- Attach a cost center, project code, and budget overrun alerts: Each invoice is linked to a project, department, or campaign, ensuring accurate spending control.
- Save the duplicate processing record: All operations are saved in the system for later use. tax audit or inspection.
The system can automatically categorize duplicate invoices by risk level, vendor, and branch, helping CFOs and accountants prioritize processing them.
10.3. Actual Results
By implementing Bizzi, businesses can achieve the following:
- Reduced 95% manual duplicate entry errors.
- Save 70–80% time on invoice reconciliation.
- Reduce the risk of tax penalties. and increase financial transparency.
💡 Insight: Bizzi not only error detection but also Prevent duplication from the data entry stage., ensuring each invoice It can only be processed once., in compliance with proper procedures and legal requirements.
11. Frequently searched user questions
1. Do duplicate invoices need to be canceled?
Yes. According to Article 11, Decree 123/2020/ND-CPDuplicate electronic invoices need to be canceled using the provided form. 04/SS-HDDT and send it to the tax authorities.
💡 Act: Fill out form 04/SS-HĐĐT above GDT Electronic Invoice Portal and keep a copy of the audit trail.
2. How are duplicate electronic invoices handled?
- If not yet declared: cancel directly using form 04/SS-HĐĐT.
- If already declared: create Declaration form for adjusting/reducing duplicate invoicesThis ensures that the right to deduct VAT is not lost.
Reference Circular 78/2021/TT-BTC Regarding the declaration and adjustment of electronic invoices.
3. Can duplicate entries be adjusted after submission?
Yes. Businesses can set it up. amended declaration form for the month of discovery To correct the input VAT figures.
💡 Tip: Combining invoice reconciliation ↔ ERP ↔ accounting software helps detect discrepancies early and reduce penalty risks.
4. What is the deadline for reporting errors?
According to Article 15, Decree 123/2020The following steps should be taken to notify the public of errors in electronic invoices: immediately after discoverymaximum 30 days from the invoice date.
5. Will I be penalized for declaring duplicate input data?
Yes. The penalty is as follows... Decree 125/2020/ND-CP:
- Duplicate entries that have not been declared: 2–4 million VND.
- Duplicate tax declarations can lead to tax errors of 5–8 million VND.
💡 Tip: Prevention is achieved through internal control procedures and automated software for detecting duplicates.
6. Which software automatically detects duplicate invoices?
Bizzi IPA + Bizzi Expense:
- Automatic duplicate detection by number, tax code, date, value, and content (fuzzy matching).
- Automatically lock suspicious duplicate transactions, provide real-time alerts, and save audit trails.
- Integration 3-way matchingInvoice ↔ Purchase Order ↔ Grand Prize.
12. Conclusion
Invoice duplication errors not only cause problems for businesses Loss of VAT deduction rights., which also increases risk of administrative penaltiesThis affects financial reporting and reputation. However, this problem is entirely preventable by strict internal control procedures combine automatic technology.
An effective strategy consists of two steps: first, How to handle duplicate invoices In accordance with regulations, when a duplicate invoice is detected, the duplicate invoice should be canceled using form 04/SS-HĐĐT, and the tax return should be adjusted if the invoice has already been declared. Decree 123/2020 and Circular 78/2021; Monday, Proactive prevention with technology through Bizzi AI + IPA + 3-way match To automatically detect duplicate invoices, block unverified expenditures, reconcile Invoice ↔ Purchase Order ↔ Grand Prize, and save audit trail for auditing.
Implementing these two steps minimizes risk and ensures that each invoice is processed correctly. one time onlyFollowing proper procedures, complying with legal requirements, and maintaining financial transparency.
Experience Bizzi now! – A solution that helps accountants automatically detect, process, and prevent duplicate invoices in seconds, ensuring financial compliance and transparency.
