Cost of goods sold audit services are becoming an urgent need for many manufacturing and trading businesses in Vietnam, especially after... Corporate Income Tax Law 2025 (Law No. 67/2025/QH15) takes effect from October 1, 2025 and Decree 320/2025/ND-CP Detailed guidelines were issued on December 15, 2025. These two documents tighten the conditions for recognizing deductible expenses, with selling expenses including commissions, advertising, transportation, and promotions being a group of items easily disallowed by tax authorities due to lack of valid documentation or incorrect accounting.
In reality, many businesses are required to pay back hundreds of millions of VND simply because their sales expenses lack proper contracts, invoices are invalid, or exceed established limits without clear justification. This article analyzes the legal nature, standard procedures, and common risks involved in auditing sales expenses, along with practical experience from the team of experts at MAN – Master Accountant Network, with over 30 years of experience in auditing, accounting, and taxation in Vietnam.
What is a cost of sales audit service? What is its legal nature?
According to Circular 200/2014/TT-BTC, selling expenses are all actual costs incurred in the process of selling products, goods, and services, and are accounted for in account 641. This item includes sales staff costs, packaging material costs, tools and equipment costs, depreciation of fixed assets used for sales, product warranty costs, and costs of outsourced services such as advertising, agent commissions, and transportation of goods to customers.
The cost of goods sold audit service is an activity performed by an independent auditing firm or internal control department to verify documents, compare contracts, and check the consistency between accounting data and the regulations in Article 9 of the Corporate Income Tax Law 2025. The ultimate goal is to ensure that expenses are recorded correctly and qualify as deductible expenses when determining taxable income.
Unlike a comprehensive financial statement audit, a sales cost audit focuses specifically on a group of items with high transaction frequency, numerous small suppliers, and susceptibility to subjective judgment. Therefore, the scope of work usually delves deeper into each original document rather than simply using a sampling method like a comprehensive audit.
What items are included in the cost of goods sold?
- Costs include salaries, bonuses, and commissions for employees and sales agents.
- Advertising, marketing, promotional, and trade show expenses.
- Costs for transportation, loading and unloading, and packaging of goods.
- Costs for product warranty and after-sales service.
- Depreciation costs of fixed assets used in sales operations.
- Other outsourced service costs directly related to product consumption.
Why do businesses need sales cost auditing services?
From October 1st, 2025, Article 9 of the 2025 Corporate Income Tax Law and Decree 320/2025/ND-CP will stipulate stricter requirements for supporting documents, including a proposal to lower the threshold for invoices that must be paid using non-cash methods to be considered deductible expenses. Selling expenses, which are dispersed across many departments and small suppliers, are the group most prone to documentation errors in the entire financial statement.
From the perspective of MAN – Master Accountant Network, after years of advising medium and large-scale manufacturing and distribution businesses, most errors do not stem from fraud but from a lack of internal control procedures when recording commission and promotional expenses. Sales expense audit services help detect these loopholes before tax authorities intervene, thereby significantly reducing the risk of back taxes and penalties.
Beyond compliance objectives, sales cost audits offer managerial value. When each expense is reviewed periodically, management has accurate data to assess the effectiveness of each sales channel and promotional program, rather than simply looking at the total cost on the income statement. This benefit is often overlooked when businesses view audits merely as a compliance procedure.
See more articles at: Top 10 Reputable and Professional Auditing Service Companies in Ho Chi Minh City
What risks does a business face if it doesn't conduct an audit of its cost of goods sold?
- Having all or part of an expense disallowed during corporate income tax settlement increases the amount of tax payable.
- Late payment penalties will be calculated on a daily basis on the amount of back taxes collected, as stipulated in the Tax Administration Law.
- Administrative penalties will be imposed for violations related to invoices and documents if systematic irregularities are discovered.
- Lack of transparency in expense records can negatively impact financial credibility when raising capital, obtaining bank loans, or conducting M&A.
What is the process for conducting a sales cost audit?
A professional cost of sales audit service needs to follow a standardized process to ensure objectivity and full legal basis. Below is the six-step process that MAN applies to the majority of its corporate clients.
- Step 1: Preliminary survey and document collection. The auditor works with the accounting and sales departments to gather books, contracts, and invoices related to sales expenses during the period.
- Step 2: Reviewing documents and comparing them with contracts. Each expenditure is compared with the contract, acceptance report, and payment documents to determine its validity.
- Step 3: Verify the reasonableness of expenditures against industry standards and internal company regulations, identifying any unusual expenses or expenditures exceeding approved limits.
- Step 4: Compare current tax regulations, including Article 9 of the Corporate Income Tax Law 2025 and Decree 320/2025/ND-CP, to determine which expenses are eligible for deduction.
- Step 5: Prepare an audit report on the cost of goods sold, clearly stating the findings, the level of risk, and recommendations for accounting adjustments or additional documentation.
- Step 6: We will assist businesses in providing explanations to tax authorities if audits or inspections arise after the tax settlement period.
By fully adhering to the six steps above, the cost of sales audit service goes beyond simply detecting errors; it also helps businesses rebuild sustainable internal control processes for subsequent accounting periods.
See more articles at: Reputable auditing firms: Top 15 leading firms and solutions from MAN
What does MAN – Master Accountant Network's sales cost audit service include?
The solutions from MAN – Master Accountant Network are designed for thorough problem-solving, going beyond simply identifying errors and providing specific corrective advice. MAN's team of auditors holds Certified Public Accountant (CPA) certifications issued by the Ministry of Finance and possesses practical experience handling documentation for FDI and domestic businesses across various sectors including manufacturing, trade, and services.
Each audit service contract MAN's sales fees come with a commitment to client confidentiality and clear legal liability for the delivered audit results. Below are sample service packages, flexibly designed to suit the size and complexity of each business.
Clients who choose MAN's sales cost audit services are typically businesses that have previously encountered difficulties with tax settlement, or businesses that have recently expanded their distribution channels and want to establish cost control processes from the outset, avoiding future problems.
| Service package | Scope of work | Execution time | Reference cost |
| Basic Package | Review sales expense documents using a selected template and compare them with the main contract. | 5-7 business days | According to the agreement, the calculation will be based on the volume of documents. |
| Advanced Package | Audit all documents, compare them with current tax regulations, and prepare a recommendation report. | 2-3 weeks | According to the agreement, a price quote will be provided after the survey. |
| Comprehensive Package | Auditing multi-branch sales expenses, and assisting with tax explanations after the audit. | 4 weeks or more | According to the agreement, pricing is based on scale. |
The above price list is for reference only; the actual cost will be surveyed and quoted specifically by MAN depending on the transaction scale, number of documents, and complexity of each company's accounting system.
Case study: How do distribution businesses in District 7 handle selling expenses?
Context: Company Y, a distributor of fast-moving consumer goods in District 7, has a network of over 200 agents nationwide. Agent commissions and promotional expenses account for nearly 181% of monthly revenue, but the majority are recorded based on internal statements, lacking standardized agency contracts.
Handle: After using MAN's sales cost audit service, the company received guidance from the audit team on three main things: standardizing agency contract templates with clear commission clauses, developing internal promotional regulations approved for each program, and digitizing all commission payment documents for monthly reconciliation.
Result: After two quarters of implementation, the company reduced the number of invoices deemed ineligible for deductible expenses by approximately 65%, and shortened the year-end tax settlement period from three weeks to one week thanks to the sales expense records being audited and fully organized in advance.
Expert analysis of common risks when conducting sales cost audits.
Experts at MAN – Master Accountant Network, with over 30 years of practical experience in tax risk management in Vietnam, point out three of the most common risk groups when businesses handle sales expenses themselves without the support of professional auditing services.
- Risk 1: Recording commission expenses exceeding the agreed-upon rate in the agency contract, or lacking a written contract, is the most common mistake when businesses rapidly expand their distribution channels without having completed the necessary legal documentation.
- Risk 2: Promotional expenses that lack program approval or registration in accordance with commercial regulations may lead tax authorities to question the legitimacy of the entire expenditure.
- Risk 3: Combining selling expenses and administrative expenses into a single account makes it difficult to audit selling expenses, which need to be separated and compared with their corresponding revenue.
A practical piece of advice often shared by experienced auditors at MAN is to review sales expenses by promotional campaign or dealer partnership, rather than aggregating them monthly, as this approach helps detect anomalies much earlier than waiting until the end of the year to consolidate them.
Legal documents related to selling expenses.
To determine deductible selling expenses for corporate income tax purposes, businesses need to simultaneously refer to regulations on taxation, accounting, documentation, and auditing. Important legal documents include: the Corporate Income Tax Law 2025, Decree 320/2025/ND-CP, Circular 200/2014/TT-BTC, the Independent Auditing Law 2011, and the Tax Administration Law 2019.
| Legal documents | Number / Validity | Related content |
| Corporate Income Tax Law 2025 | Resolution No. 67/2025/QH15, effective October 1, 2025 | Article 9 specifies the conditions under which expenses are deductible and non-deductible. |
| Decree 320/2025/ND-CP | Issued on December 15, 2025 | Detailed instructions on documentation requirements and cases of purchasing goods without invoices. |
| Circular 200/2014/TT-BTC | Ministry of Finance, December 22, 2014 | Guidelines for business accounting procedures and accounting for sales expenses. |
| Independent Auditing Law 2011 | No. 67/2011/QH12 | Regulations on the scope and operating principles of independent auditing in Vietnam. |
| Tax Administration Law 2019 | No. 38/2019/QH14 | Regulations on penalties for late payment and handling of violations when collecting back taxes. |
Conclude
Sales expense audit services not only help businesses comply with the Corporate Income Tax Law 2025 but also serve as an effective internal control tool, helping to retain deductible expenses and minimize the risk of being subject to retroactive tax collection during final settlement. The more proactively businesses conduct audits, the lower the risk becomes.
MAN – Master Accountant Network is ready to partner with businesses in reviewing, standardizing, and optimizing sales expense records, with a team of CPA experts boasting over 30 years of practical experience in Vietnam. Contact MAN today for a free survey and consultation on sales expense auditing services tailored to your business size.
Other services
- Internal audit services
- Internal Control System Assessment Service
- Auditing services on request
- Professional tax audit services
- Construction auditing services
- Completed project settlement audit service
- Financial statement audit services
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
- E-mail: man@man.net.vn
- Google Business Profile: View MAN – Master Accountant Network's Google Business Profile
- LinkedIn Founder: View expert Le Hoang Tuyen's LinkedIn profile.
Responsible for production and professional content review by: Mr. Le Hoang Tuyen – Founder & CEO of MAN – Master Accountant Network, CPA Vietnam with over 30 years of experience in accounting, auditing, taxation, and corporate financial consulting.
Frequently Asked Questions about Cost of Goods Sold Audit Services
What size of business is suitable for cost of sales audit services?
Suitable for businesses of all sizes that incur significant selling expenses, especially those with large dealer networks, advertising, or promotional costs. Newly established small businesses should also consider using selling expense auditing services from the outset to establish proper documentation procedures.
How long does it take to perform a sales cost audit?
Depending on the volume of documents, typically from one to four weeks per accounting period, a comprehensive package may take longer if the business has multiple branches.
Is auditing the cost of sales mandatory by law?
While not mandatory for typical businesses, it is an essential risk control tool before tax settlement or when preparing M&A documents.
Are sales expenses without invoices acceptable during an audit?
In some cases, purchases without invoices can still be considered deductible expenses under Decree 320/2025/ND-CP if valid substitute documents are available, provided they are specifically verified by an auditor.
Do FDI businesses need separate sales cost auditing services?
Yes, because FDI enterprises often have transactions with related parties, selling expenses need to be compared with regulations on related-party transactions to avoid the risk of tax assessment.
