Tax Health Check Before the Revenue Calls in Thailand

Reconciling PND 50 to the financial statements line by line

A filed PND 50 should reconcile back to the profit-and-loss statement and the balance sheet on every line, not merely at the net-profit total. The usual slippage sits in the adjustments that turn accounting profit into taxable profit: depreciation computed at a different rate than the Revenue Code allows, a bad-debt provision set above the permitted threshold, and Section 65 Ter add-backs that some companies simply forget to include on the return. Once a reconciliation shows the filed figure and the ledger figure diverging with no working paper to explain why, that is usually the first thing an assessment officer asks about.

A second reconciliation point covers exempt or specially taxed income: dividends exempt under shareholding conditions, deposit interest already subject to withholding, and BOI-promoted income that must sit in separate accounts from non-promoted activity. Companies running both promoted and ordinary lines within one legal entity often blend shared costs without a written allocation rule, so when documents are actually requested there is no basis to explain the split. A health check therefore walks the cost-allocation method alongside the return figures, not after them.

The last item in this area is retrospective adjustment: financial statements amended after filing, or expenses discovered to have been double-posted or booked in the wrong year. Left unaddressed, these compound across years because a wrong retained-profit base keeps rolling forward. A proper health check therefore does not stop at the latest year; it looks back at least three years to see whether a discrepancy is a one-off or a recurring pattern.

Reconciling VAT filings against actual revenue

The PP30 returns filed each month should sum to the annual sales figure in the profit-and-loss statement. The usual gap comes from income that carries no tax invoice — interest income, exchange gains, or other receipts outside the VAT system. Without a clear schedule separating VATable revenue from non-VATable revenue, when a reviewer lines up total sales in the financial statements against cumulative PP30 sales and the numbers do not match, the burden of explaining the gap falls immediately on the company.

Another point to watch is timing: output tax invoices issued in a different month from actual delivery, particularly for businesses that bill in advance or collect payments in instalments. The timing gap is not evasion, but it does build a running difference that must be explained month by month. On the input side, the recurring problem is claiming input VAT on defective invoices — a buyer's tax ID entered incorrectly, or invoices from a seller who had already deregistered — which the law disallows even where payment genuinely occurred.

Businesses with multiple branches, or that transfer goods between branches, need particular care, because a transfer of goods between establishments filing VAT separately is treated as a deemed sale requiring its own tax invoice. Where this is not recorded consistently, total output VAT ends up understated without anyone intending it. This part of the health check should therefore reconcile by branch and by revenue category, not only at the company-wide total, because the discrepancy usually hides at branch level.

Completeness of withholding tax under PND 3, 53 and 54

Withholding-tax duties are easy for a company to overlook because the tax is not one it pays out of its own pocket, but the liability as the withholding agent is no lighter for that. Failing to withhold on service fees, contract work, rent, or professional fees makes the company jointly liable with the payee for the shortfall plus surcharge. A health check must walk every expense account that triggers withholding and compare it against the PND 3 return for individual payees and the PND 53 return for corporate payees, checking that amounts actually paid match the base used to compute the withholding.

PND 54, covering payments of income and profit remitted abroad, carries steep exposure when neglected, particularly for companies transacting with an overseas parent or affiliate — royalties, consulting fees, loan interest, or dividends repatriated. The rate to withhold can differ under Thailand's double-tax treaties with the counterparty country, and where a company applies a treaty-reduced rate without keeping the payee's certificate of tax residence on file, a later review typically reassesses at the standard rate rather than the treaty rate, with surcharge running from the original due date.

A more common structural failure than misapplying the rate is withholding correctly but remitting late, or withholding in full but not issuing a withholding certificate for every payment. Neither directly changes the tax remitted, but both create counterparty complaints and documentation gaps once a review reaches back. A health check should therefore sample withholding certificates against the general ledger, not merely check the amount remitted to the Revenue Department.

Disallowed expenses and the documentation gaps behind them

Most expenses disallowed on review are not unlawful in themselves; they simply lack adequate support — client entertainment with no attendee list or stated business purpose, travel costs with no original receipt or one that names no company, and purchases from small vendors paid in cash with no full tax invoice. Accumulated across years these can become a material sum, and reviewers tend to drill into categories that are large relative to revenue.

A second group carries statutory conditions of its own: passenger-car depreciation capped at a maximum cost base, interest paid to directors or shareholders that needs a loan agreement and a market-comparable rate, and losses on asset sales to related parties below market value, which the law lets an assessment officer re-price. Many companies record these correctly under accounting standards but never make the corresponding tax add-back on the return, building up risk without anyone noticing.

Closing these gaps should not be a once-a-year scramble before the books close, since documents from prior periods are far harder to trace than current-year ones. What works is setting a minimum document checklist for each expense category in advance and having purchasing and accounting verify completeness before posting, not after an auditor or assessment officer asks, by which point the staff who knew the background may already have left.

Related-party transactions

Transactions between a company and its directors, shareholders, or affiliated companies draw particular attention from assessment officers, because the price or interest rate involved may not reflect an arm's-length market rate — interest-free or below-market intercompany loans, goods or services sold to a related party more cheaply than to ordinary customers, or assets leased from a director at an inflated rent. In each case the Revenue Code gives the officer authority to re-price income or expense at market value, typically bringing several years of additional tax and surcharge with it.

The health check should start by compiling a complete list of related individuals and entities, then pull every transaction with those parties over the past three years to compare the price used against market or third-party rates. Many mid-sized companies have no written intercompany pricing policy, so even where the price actually used is reasonable, there is nothing on file to support the reasoning when asked. Preparing a note explaining the pricing rationale in advance is worth far more than trying to reconstruct it after a review has already started.

For companies transacting with an overseas affiliate, transfer pricing adds complexity because both Thai rules and the counterparty jurisdiction's rules apply at once. Companies above the statutory revenue threshold must file an annual related-party transaction report and may need contemporaneous transfer-pricing documentation on hand. The health check should confirm whether the company has crossed that threshold and, if so, whether the documentation on file is genuinely substantive or merely a template filled in without the underlying analysis behind it.

Inventory and cash irregularities

A closing inventory figure that does not tie to an actual physical count is a signal that assessment officers weigh heavily, because a shortfall can be read as unrecorded sales on which output VAT was never remitted, while an unexplained surplus can be read as fictitious purchases inflating cost of goods. Either direction leads to a reassessment computed by comparing the company's gross margin against the industry average — a method the Revenue Department reaches for often when it cannot pin down the actual cause of a gap.

The health check should therefore reconcile book inventory against a physical count at least once a year, and confirm that damaged, expired, or obsolete stock has been written off with proper destruction evidence or approval records. Writing off inventory without supporting evidence is typically disallowed as an expense, and it also leaves the book-to-physical gap unresolved for the next period.

On the cash side, a company holding cash disproportionate to daily sales, or accepting cash from customers without issuing a receipt at the point of sale, tends to draw suspicion of unrecorded revenue, particularly in retail and food-service businesses running mainly on cash. What reduces the risk is reconciling cash received against the daily sales report every day rather than every month, and keeping bank-deposit evidence timed consistently with when the cash was actually collected, so the cash trail can be explained from origin to deposit.

Self-correction and voluntary amended filings before an inspection arrives

Once a health check finds an error the Revenue Department has not yet flagged, the company can voluntarily file an amended return and pay the shortfall plus the statutory surcharge — materially different from being caught first, because a voluntary correction generally avoids the penalty computed as a percentage of the shortfall, whereas an assessment raised by an officer can carry a penalty of up to one or two times the shortfall depending on the circumstances. The cost gap between the two paths is large enough on its own to justify correcting first.

Amended filings should be handled systematically, not patched one item at a time as errors are stumbled upon, because repeated piecemeal corrections can make it look as though internal controls are worse than they actually are. The better approach is to gather every finding from a single health-check cycle, rank them by risk and amount, and plan the corrective filings — with tax and surcharge paid — in one coordinated batch, backed by an internal memo explaining the cause and the preventive step taken, in case a later review of a different year raises questions about an item already corrected.

The limitation to know is that self-correction loses most of its benefit once the Revenue Department has already issued a notice or begun a review on that specific issue, because the penalty relief is generally tied to acting before the officer starts. A health check therefore delivers the most value while there is no sign of an impending review, not after a summons has already arrived, by which point the self-correction route is usually closed off for whatever issue that notice names.

Modelling surcharge exposure and planning the cash flow to cover it

Surcharge under the Revenue Code accrues monthly from the day after the filing deadline until actual payment, capped at the tax amount due, so the longer an uncorrected error sits, the more its cost compounds. A proper health check should come with an estimated surcharge figure for each finding, comparing correcting now against leaving it another year, so management sees a tangible cost rather than a general recommendation.

The cash-flow plan to cover this should split into two components: the underlying tax shortfall, a fixed amount determined by the finding, and the surcharge, a variable driven by how long correction takes. Companies with errors accumulated over several years may find total surcharge actually exceeds the underlying tax due, especially past the three-year mark. Prioritising correction should therefore start with the item accruing surcharge fastest, even where the underlying tax amount is not the largest one on the list.

For companies with cash constraints unable to pay the full shortfall and surcharge at once, the Revenue Department offers instalment arrangements in some cases, which should be negotiated at the same time as the amended filing rather than after a collection demand arrives. Negotiating while the company is the one coming forward tends to be treated more flexibly than negotiating after being pressed for payment, and it also demonstrates the good faith that can bear on the discretion available in the limited cases where surcharge reduction is legally possible.

When to act, and when waiting is fine

• PND 50 has never been systematically reconciled to the financial statements

  Start a three-year retrospective reconciliation before anything else, since exposure usually spans more than one year

• There are transactions with directors, shareholders, or an overseas affiliate

  Put an intercompany pricing policy in writing and check whether the revenue threshold for the annual related-party report has been reached

• Cash makes up a large share of sales

  Reconcile cash received against the daily sales report every day and time deposit evidence to match, rather than reconciling only at month-end

• A health check finds an error but no Revenue Department letter has arrived yet

  File the amendment and pay the shortfall plus surcharge as soon as possible, since penalty relief is tied to acting before discovery