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Corporate Income Tax, Tax News | March 17, 2026 | 15-minute read

How to fill out the supplementary corporate income tax return.

Cách làm tờ khai bổ sung quyết toán thuế TNDN

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The process of filing a supplementary corporate income tax return is crucial for all accountants to master when errors are discovered in previously submitted tax documents. Following the correct supplementary procedure not only helps businesses comply with the law but also minimizes penalties for late payment or incorrect declarations as stipulated in the 2019 Tax Administration Law.

In the context of increasingly stringent tax audits, understanding how to file a supplementary tax return is crucial. corporate income tax settlement This helps businesses to self-assess and correct errors promptly. Based on Article 47. Tax Administration Law No. 38/2019/QH14, Taxpayers have the right to submit supplementary tax returns within a 10-year period, provided that it is done before the tax authorities announce a decision to conduct an on-site inspection.

Legal basis and timing for filing a supplementary corporate income tax return.

Cơ sở pháp lý và thời điểm cần thực hiện cách làm tờ khai bổ sung quyết toán thuế TNDN
Legal basis and timing for filing a supplementary corporate income tax return.

To accurately prepare a supplementary corporate income tax return, accountants need to refer to current legal documents. Specifically, the regulations on supplementary declarations are clearly stated in the 2019 Tax Administration Law and detailed instructions are provided in [link/website]. Circular 80/2021/TT-BTC of the Ministry of Finance.

The application of the method for submitting supplementary tax return forms. corporate income tax This is done when a business discovers discrepancies in revenue, expenses, or tax incentives. This often occurs after an accountant reviews documents, receives omitted input invoices, or discovers errors in classifying deductible and non-deductible expenses.

Cases where additional work is done before the inspection decision is made.

When businesses discover errors themselves, filing a supplementary corporate income tax return at this time can help mitigate legal liability. If the supplementary filing increases the amount of tax payable, the business only needs to pay the full amount of tax and late payment penalties without being subject to administrative penalties for the incorrect declaration.

Additional actions may be taken after an inspection decision has been made.

If the tax authorities have already announced a decision to conduct an on-site inspection, taxpayers can still file a supplementary corporate income tax return. However, in this case, the business will be subject to administrative penalties as stipulated in Articles 142 and 143 of the Law on Tax Administration, depending on the actual severity of the violation.

Steps for preparing a supplementary corporate income tax return using the HTKK software.

The process for filing a supplementary corporate income tax return primarily involves using the Tax Declaration Support Software (HTKK). This technology minimizes calculation errors and ensures the file format is standardized (XML) when submitted online. Below is a summary of the process for your easy reference:

Summary of the steps for preparing a supplementary corporate income tax return using the HTKK software.
Steps to take Main job responsibilities Important Note
Step 1 Log in and select form 03/TNDN. Select the tax period to be added.
Step 2 Select the status of the Supplementary Declaration. Enter the exact number of additions.
Step 3 Adjust the figures directly on the declaration form. The difference will automatically switch to KHBS.
Step 4 Prepare supplementary declaration explanation form 01-1/KHBS Clearly state the reason and details of the adjustments.
Step 5 Generate XML and submit it through the Thuedientu portal. Verify the digital signature before submitting.

Step 1: Access the system and create a profile.

To begin preparing the supplementary corporate income tax return, open the HTKK software and enter your company's tax code. In the "Corporate Income Tax" menu, select "Corporate Income Tax Final Settlement Declaration (03/TNDN)". The system will prompt you to select the tax period; choose the fiscal year with the error that needs correction.

Step 2: Select the type of declaration and the number of supplementary submissions.

In the tax period selection interface, instead of selecting "Initial Declaration," you should check the box "Supplementary Declaration." This is the key point in preparing a supplementary corporate income tax return. You need to correctly enter the number of supplementary declarations so that the system can accurately manage the company's amendment process.

Step 3: Adjust the indicators on form 03/TNDN.

After accessing the interface, you need to correct any errors in the fields. The process for filing a supplementary corporate income tax return requires you to enter the correct data into the corresponding fields. For example, if deductible expenses were underdeclared, you need to re-enter the correct total amount in field B4.

Step 4: Complete the explanation form 01-1/KHBS

The system will automatically compile the data into forms 01/KHBS and 01-1/KHBS. Here, the process of filing a supplementary corporate income tax return requires you to provide a detailed explanation of the change. You need to clearly state: "Due to missing input invoices" or "Due to incorrect determination of taxable revenue".

Step 5: Export data and submit the application online.

This is the final step in preparing the supplementary corporate income tax return. After checking the information, click "Save" to save the data and "Export" to get the XML file. Finally, log in to the portal. thuedientu.gdt.gov.vn To submit additional files and perform electronic signing as required.

Documents and procedures involved in filing a supplementary corporate income tax return.

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Documents and procedures involved in filing a supplementary corporate income tax return.

A complete supplementary tax return demonstrates transparency. When filing a supplementary corporate income tax return, accountants need to prepare supporting documents to explain the changes in figures to the tax authorities during periodic audits or inspections.

According to Circular 80/2021/TT-BTC, the standard set of documents includes the adjusted tax return form 03/TNDN, the supplementary tax return form 01/KHBS, and the explanation form 01-1/KHBS. All documents and records related to the adjusted figures must be carefully stored at the enterprise for future verification purposes.

Thorough preparation of documents when filing a supplementary corporate income tax return helps businesses be more proactive. If tax payable arises, businesses need to pay the money immediately to stop the calculation of late payment penalties at the rate of 0.03% per day on the overdue amount as stipulated by law.

Notes on late payment penalties when preparing supplementary corporate income tax returns.

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Notes on late payment penalties when preparing supplementary corporate income tax returns.

Determining late payment penalties is a crucial part of preparing a supplementary corporate income tax return. The HTKK software supports automatic calculation based on indicators M1 (number of days late) and M2 (amount of late tax). However, accountants need to double-check to ensure accuracy.

If the process of filing a supplementary corporate income tax return results in a reduction in the amount of tax payable, the business will not be required to pay late payment penalties. Conversely, any overpayment will be offset against the next tax period or refunded according to current tax regulations.

How to calculate the actual late payment penalty.

Late payment penalty = Amount of tax overdue x 0.03% x Number of days overdue

The number of days of late filing is calculated from the day following the last day of the tax filing deadline to the date the tax is paid into the state budget. Understanding this formula is an essential part of preparing a supplementary corporate income tax return.

The importance of verification before filing a supplementary corporate income tax return.

Before filing a supplementary corporate income tax return, accountants need to conduct a comprehensive review. This includes comparing the general ledger with invoices, checking the validity of welfare expenses, entertainment expenses, and any accruals that lack sufficient supporting documentation.

Common errors that necessitate filing supplementary corporate income tax returns include: revenue recorded at the wrong time, salary expenses lacking supporting documentation, or interest expenses exceeding the limit for businesses with related-party transactions as stipulated in Decree 132.

Understanding these weaknesses helps accountants prepare supplementary corporate income tax returns more effectively. Instead of waiting for retroactive collection, voluntarily adjusting the tax returns demonstrates high compliance and builds credibility for the business with the tax authorities.

Conclude

Knowing how to prepare a supplementary corporate income tax return is a mandatory skill for professional tax accountants. Mastering the process, from identifying errors to operating the tax declaration system (HTKK), will help businesses minimize legal risks and optimize costs. Properly preparing a supplementary corporate income tax return also protects the legitimate rights of the entity against stringent regulations.

To ensure the security of your tax records, businesses should seek the services of professional consultants. MAN – Master Accountant Network proudly offers auditing services., tax accounting, tax consulting, tax settlement and tax reporting In-depth expertise. We support businesses in accurately preparing supplementary corporate income tax returns and developing effective long-term tax plans. Contact MAN today to receive advice from our leading team of tax risk management experts.

Service contact information at MAN – Master Accountant Network

  • Address: No. 19A, Street 43, Tan Thuan Ward, Ho Chi Minh City
  • Mobile/Zalo: 0903 963 163 – 0903 428 622
  • Email: man@man.net.vn

Content production by: Mr. Le Hoang Tuyen – Founder & CEO MAN – Master Accountant Network, Vietnamese CPA Auditor with over 30 years of experience in Accounting, Auditing and Financial Consulting.

Frequently Asked Questions about How to File a Supplementary Corporate Income Tax Return

Can a business file multiple supplementary tax returns for the same tax period?

Yes, businesses are allowed to file supplementary corporate income tax returns multiple times if they discover further errors, as long as it is before the tax authorities announce a tax audit decision.

What is the deadline for submitting supplementary corporate income tax returns?

The deadline for submitting a supplementary corporate income tax return is 10 years from the date the original filing deadline expires, but it must be before a tax audit decision is issued by the tax authorities.

If filing an amended tax return reduces the tax payable, will I receive an immediate refund?

In cases where filing a supplementary corporate income tax return results in a tax reduction, the overpaid amount can be offset against other taxes or in a later period, or the business can apply for a refund of the overpaid tax.

Do I need to resubmit the appendices that accompanied Form 03 Corporate Income Tax when filing a supplementary declaration?

When submitting a supplementary corporate income tax return, you need to include the relevant appendices detailing the adjustments to ensure data consistency within the system.

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