Carrying losses forward looks like an automatic right of a genuinely loss-making enterprise, but the right is eroded by very small technical mistakes: forgetting to declare the carryforward one year, carrying in the wrong order, or using the audited loss instead of the tax-finalised loss. Only when the authority rejects the entire carried loss does the enterprise look back in alarm. This article lists the mistakes that forfeit carryforward rights, explains why audited and tax losses never fully coincide, and sets out the appeal route when a rejection decision is issued.
The carryforward right, and how technical mistakes destroy it
Under the Law on Corporate Income Tax 67/2025/QH15, a loss arising in a tax period may be carried into the income of subsequent years, with the carryforward period not exceeding five consecutive years from the year following the loss year; after five years, any uncarried remainder lapses permanently. The enterprise self-determines the loss and the carryforward through the loss carryforward appendix attached to the annual finalisation return, carrying in order of the earliest loss year first. Losses of incentivised and non-incentivised activities must be accounted separately and carried separately, without offsetting each other.
The most common forfeiting mistake is a declaration gap: in a profitable year the enterprise forgets to declare the carryforward in that year’s appendix — because carryforward works continuously, the authority treats the corresponding loss as abandoned in the skipped year and refuses later carryforward. The second mistake is wrong order: using newer losses first while an older loss near its five-year expiry hangs unused, wasting the old loss to expiry. The third is failing to update later years’ appendices after an assessment changes the original year’s loss, creating a contradictory data chain rejected wholesale when an inspection reconciles it.
Why audited losses differ from tax losses, and where to appeal
The loss in audited financial statements and the tax loss differ systematically, because the two systems measure two different things. The accounting loss includes every expense under accounting standards — including items tax disallows such as uninvoiced costs, fines, welfare spending above the cap and excess depreciation; the tax loss is the result after adding back non-deductible expenses, removing not-yet-taxed income and applying tax revenue recognition rules. The loss carried forward is the adjusted finalised tax loss, not the loss printed in the audit report. At finalisation, the enterprise explains this gap through the upward and downward taxable-income adjustment table on the return and an appendix detailing each material difference — a working document maintained with auditors and the tax authority routinely, not something to start when asked.
When the tax authority issues an assessment decision or a notice refusing the carried loss, the enterprise complains against that decision at the issuing tax authority within 90 days under the Law on Complaints, with a proof file comprising the returns and carryforward appendices of all relevant years, inspection minutes of the origin years and a year-by-year accounting-versus-tax loss reconciliation. While the complaint is pending, later years’ finalisation returns should still declare the carryforward on the enterprise’s position with a dispute note, because skipping declaration while awaiting the complaint is precisely the gap mistake that forfeits the right permanently — even if the complaint succeeds.
Conclusion and recommendations
Loss carryforward is a right with a double expiry: it lapses after five years, and it lapses after one skipped declaration year. An enterprise with accumulated losses should keep a living carryforward schedule — tracking each loss by origin year, its five-year deadline and amounts carried each year — reconciled every finalisation season across accounting, audit and tax files. Such a schedule costs far less than discovering the right is lost when the rejection decision is already on the desk.
Frequently asked questions
1. What is the maximum loss carryforward period?
A maximum of five consecutive years, from the year following the loss year, under the Law on Corporate Income Tax 67/2025/QH15. The enterprise must carry the full loss into income years in origin-year order and may not pick years to carry intermittently; when the five-year term for a given loss expires, the uncarried remainder loses value. Note that the loss carried is the finalised tax loss of the origin year, and losses of tax-incentivised activities must be tracked and carried separately from losses of non-incentivised activities.
2. What mistakes lose the loss carryforward?
Four common mistakes. One, a declaration gap: skipping one year’s carryforward declaration in the appendix of a profitable year, so the corresponding loss is treated as abandoned and cannot be carried later. Two, wrong order: not carrying in origin-year order, so the old loss hits its five-year expiry while still intact. Three, wrong loss basis: carrying by the financial statement loss instead of the adjusted finalised tax loss. Four, failing to update the file chain when the authority reassesses the origin year’s loss, leaving later appendices contradictory and rejected. All four are filing-process mistakes, entirely preventable with a continuously maintained carryforward schedule.
3. An independent auditor approved a different loss — can that save it?
No, in the sense that the audit is not the carryforward basis. An independent audit report confirms financial statements under accounting standards; the tax authority accepts only the finalised tax loss after adjusting non-deductible expenses and recognition differences between the two systems. An audit helps indirectly — a quality audit file evidences the honesty of the underlying accounting figures, the starting point of the accounting-to-tax loss bridge — but if the finalisation adjustments yield a smaller or zero tax loss, the audit opinion cannot turn the accounting loss into a carried loss. What protects the carryforward right is a correct finalisation return and carryforward appendix, not the audit report.
4. Where to appeal a decision refusing the loss carryforward?
Complain at the tax authority that issued the assessment decision or the notice refusing the carried loss, within 90 days of receiving the document under the Law on Complaints. The complaint file comprises the finalisation returns and carryforward appendices of the loss year and every carry year, related inspection minutes, and an accounting-versus-tax loss reconciliation proving continuity and order. One vital note: while the complaint is being resolved, keep declaring the carryforward in subsequent years on the enterprise’s position with an explanatory note, because stopping declaration to await the outcome is the very gap mistake that forfeits the right permanently regardless of the complaint’s result.
This article has been quality-reviewed by the FLAW AI Legal Council