Lost Accounting Documents: What Should You Do? Initial Steps
The problem of lost accounting documents is a situation where key evidence of a commercial transaction, such as a purchase tax invoice, a receipt or a payment voucher, has been lost, damaged beyond legibility, or was never received as an original from the counterparty. When this happens, the business owner must take 3 main corrective steps immediately:
- Sort the lost documents by type: Distinguish between value added tax documents (purchase tax invoices), which affect VAT claims, and general expense documents used for corporate income tax.
- Request a substitute or a certified copy: Promptly write to the original counterparty to request a "substitute tax invoice" or a copy of the receipt signed to certify that it is correct.
- Prepare replacement supporting documents: If documents cannot be obtained from the counterparty, prepare internal evidence within the limits set by law, such as a receipt voucher with a copy of the payee's ID card, or a certificate in lieu of a receipt (Form Bor.Chor.3) with the transfer slip attached.
Letting documents slip through the cracks until the 2026 year-end close means those expenses will be interpreted by the Revenue Department as non-deductible and immediately added back to net profit for additional tax. Preparing correct replacement documents before filing the P.N.D.50 (corporate income tax return) within 150 days of the end of the accounting period is therefore an important step in protecting the business's interests.
Why Are Lost Accounting Documents Dangerous? Legal Consequences and the Risk of Tax Add-backs
From the standpoint of Thai law, accounting source documents are evidence of financial rights and obligations. Two main laws govern them and set out clear penalties:
- Accounting Act of 2000 (Sections 19 and 31): Requires those responsible for keeping accounts to retain the accounts and supporting documents at the place of business for at least 5 years from the closing date (the Director-General may extend this to 7 years). If documents are lost or cannot be produced during an inspection, the criminal fine is up to 20,000 baht plus a daily fine of up to 500 baht until the matter is put right.
- Revenue Code, Section 65 ter (18): Provides that "expenses for which the payer cannot prove who the recipient was" are a non-deductible expense for tax purposes. Even if the business actually paid the money and the bank statement shows the debit, without a document stating the payee's name, address and tax identification number, the assessment officer has the power to add the entire expense back to net profit.
A Real Example: The Financial Impact of Lost Documents (Case Study of a Cafe in Chiang Mai)
Cafe Nimman Co., Ltd. runs a food and beverage business in the Nimmanhaemin area of Chiang Mai. It spent a total of 100,000 baht on shop fittings and ingredients (VAT at 7% of 7,000 baht, total paid 107,000 baht), but lost all of the tax invoices and receipts and has no evidence identifying the payees.
When the auditor and Revenue Department officers examine the financial statements, the damage is calculated as follows:
- Corporate income tax add-back: The 100,000 baht expense is reclassified as non-deductible under Section 65 ter (18). If the company's net profit falls within the SME tax bracket of 15% (net profit above 300,000 baht but not more than 3 million baht), the company must pay an additional 15,000 baht in corporate income tax (100,000 × 15%).
- Input tax cannot be offset: The 7,000 baht of input tax cannot be deducted from output tax on the P.P.30 (monthly VAT return), so the full amount of VAT must be paid.
- Tax penalties and surcharges: If the company has already claimed the 7,000 baht of input tax but cannot produce the original tax invoice, it will be assessed a penalty of 1 times the tax under Section 89(4), namely 7,000 baht, plus a surcharge under Section 27 at 1.5% per month (a fraction of a month counts as a full month) on the tax due.
From just 100,000 baht of expenses with lost documents, the business ends up bearing more than 29,000 baht in extra tax, penalties and costs. Tax planning and organising a document system from the start of the period can therefore prevent significant financial losses.
5 Mistakes with Lost Accounting Documents that Risk a Tax Add-back before the Year-End Close
From our experience auditing accounts, there are 5 main mistakes that business owners tend to make when documents are lost, and they directly affect the financial statements and the tax burden:
1. Doing Nothing and Recording the Expense Anyway without Documents
A common misunderstanding is that a bank statement or a transfer slip alone is enough to record an expense. For tax purposes, a statement only shows cash flowing out; it cannot prove whether the goods or services were actually used for the business. Without a supporting document that lists the goods/services, the expense is immediately removed from the tax calculation.
2. Confusing "Income Tax Evidence" with a "Purchase Tax Invoice (VAT)"
Proof of payment used to deduct an expense for corporate income tax, and the document used to claim input tax in the VAT system, have clearly different legal conditions: claiming input tax requires an original full-form tax invoice (Section 86/4) or a substitute tax invoice (Section 86/12) only. A transfer slip or an ordinary receipt can prove payment for a corporate income tax deduction, but it can never be used to claim the 7% input tax.
3. Creating Documents after the Fact without the Real Payee's Details
When a bill is lost, some business owners fix it by writing up their own cash bill with a vague shop name and no ID number, address or tax identification number for the payee. This falls under Section 65 ter (9), "expenses determined by the taxpayer without actual payment", and Section 65 ter (18). Besides the whole amount being added back for tax, if it amounts to fabricating false evidence there is also criminal liability under the Revenue Code.
4. Not Requesting a "Substitute Tax Invoice" in Writing within the Deadline
Under Section 82/3 of the Revenue Code, input tax can be deducted from output tax within 6 months of the month in which the tax invoice was issued. If a document is lost and the business neglects to formally request a substitute from the seller until that period has passed, the business permanently loses the right to a refund or to offset that input tax.
5. Sending Documents to the Accounting Firm Too Close to the Closing Date
Gathering accounting documents and handing them to the bookkeeper in the last 1-2 weeks before the deadline for filing the financial statements and tax return (P.N.D.50) leaves the bookkeeper and auditor without enough time to check accuracy, track down lost documents, or request substitutes from counterparties. The result is having to accept the add-back and pay more tax than necessary.
Remedies and Replacement Documents When Accounting Documents Are Lost (Approaches the Revenue Department Accepts)
If accounting documents are found to be missing, the Revenue Department and the Department of Business Development (DBD) have practice guidelines that allow replacement documents to be used for correct bookkeeping and tax calculation, as summarised in the table below:
| Type of lost document | Legal steps to remedy | Replacement documents to prepare | Tax effect (VAT / corporate) |
|---|---|---|---|
| Full-form tax invoice (purchase side) | 1. Report the lost documents to the police 2. Write to the seller requesting a "substitute tax invoice" under Section 86/12 |
Substitute tax invoice (a photocopy of the original stamped "substitute" in red and signed by the seller) + copy of the police daily report | Can be used to claim input tax lawfully and as a corporate income tax expense |
| Receipt from a juristic person (not VAT-registered) | Contact the counterparty's accounting department to request a copy of the original receipt | Copy of the receipt bearing the company seal and the payee's signature certifying the copy + proof of transfer (bank slip) | Can be used as a corporate income tax expense (no effect on VAT) |
| Purchase bills from individuals / fresh markets | Prepare a "receipt voucher" (payment voucher) for the payee to sign | Receipt voucher stating name, address, items, date and amount + copy of the payee's ID card + proof of transfer to an account matching the ID card | Can be used as a corporate income tax expense under Section 65 ter (18) |
| Miscellaneous expenses for which no receipt is available (e.g. travel, motorcycle taxi fares) | Have the employee who paid prepare a "certificate in lieu of a receipt" (Form Bor.Chor.3) as soon as the transaction occurs | Form Bor.Chor.3 stating the payment details and the business purpose + signature of the payer + signature of the person authorised to approve payment | Can be used as a corporate income tax expense (as necessary and appropriate for the business) |
Accounting Services in Chiang Mai and the Move to Digital Documents
The most effective way to prevent lost documents is to change how documents are stored, moving from paper to a digital system. For business owners in the northern region, whether hotels, cafes, guesthouses or service businesses, choosing an expert accounting firm in Chiang Mai that works on an online accounting system eliminates the problem of missing documents permanently.
Working with a modern accounting firm lets you send and store documents digitally the moment a payment is made. Simply photograph the document or save the file and send it through a digital channel, and it is recorded neatly in the online accounting system. There is no need to worry about faded paper, damp documents or loss in transit, and if you have a tax question you can consult the team conveniently and quickly through the LINE application.
In addition, for retail businesses, restaurants or cafes that issue a large number of bills at the counter, choosing a monthly accounting and year-end close service that includes a point-of-sale (POS) and stock management program worth 15,000 baht (free with the monthly accounting service) makes stock control and front-of-shop income and expense documents far more accurate. The program works offline, so the data stays securely on the shop's own computer, and our team installs it and trains you on site.
Frequently Asked Questions (FAQ)
1. The receipt is lost but I have a mobile banking transfer slip. Can it be used to deduct a company expense?
Yes, it can be deducted as a corporate income tax expense, but additional internal documents must be prepared: a payment voucher with the transfer slip attached clearly showing the payee's account name, plus evidence of delivery of the goods/services, to prove that the payment was genuinely for the benefit of the business under Section 65 ter (18).
2. If the original purchase tax invoice is lost, can a photo or an ordinary copy be used to claim input tax?
No, a photo or an ordinary copy cannot be used. The law requires a "substitute tax invoice" under Section 86/12 of the Revenue Code only. The seller must photocopy the original duplicate tax invoice, stamp it with the word "substitute" and sign it; only then can it be used to support the input tax deduction on the P.P.30.
3. Accounting documents were lost through force majeure, such as flood or fire. What should I do?
You must file a police report in the daily log immediately and submit a written notice of the loss to the accounts inspector at the Department of Business Development or the Provincial Commercial Office within 15 days of the date you became aware of the loss, under Section 21 of the Accounting Act of 2000. This serves as evidence protecting the business from being assessed the statutory penalties.
4. For how many years must expense documents from past years that have already been closed be kept?
Section 19 of the Accounting Act of 2000 requires accounting source documents to be kept for at least 5 years from the closing date. However, if the business has accumulated losses carried forward or is under a tax audit by the Revenue Department, we recommend keeping them for 5 - 7 years, in line with the officers' power to assess tax retrospectively.
Summary: Handling Lost Accounting Documents and Setting Up a New Accounting System
The problem of lost accounting documents is not fatal if it is detected early and you know how to fix it within the legal framework. But if it is left until the 2026 year-end close, these expenses will come back as a heavy tax and penalty burden for the business. Setting up a digital document system together with an online accounting system is the most sustainable solution.
If you are uneasy about how documents were kept in the past, worried about tax add-backs, or feel that working with your current accounting firm is not fast or convenient enough, you can switch to a professional team that will look after your books and set up a correct document system from the start. An initial consultation is free of charge.
Contact YMTD Accounting Partner Chiang Mai
Tel: 081-542-3019
LINE: @premwittawat
