Can someone else act on your behalf for tax privileges for BOI-promoted companies, and what power of attorney is needed?
Short answer
A Thai company files PND.51 for the half-year based on an estimate of annual net profit and PND.50 for the full year based on audited accounts. Accounting profit is converted to taxable profit through adjustments for non-deductible expenses and specific tax rules.
How this case runs end to end
Close the accounts for the period, prepare the tax computation with adjustments, reconcile the tax charge to the financial statements, file PND.51 mid-year and PND.50 after the audit, and retain the supporting schedules for inspection.
Stage-by-stage timeline
| Stage | Work | Owner | Window |
|---|---|---|---|
| Preparation | Bookkeeping, computation and reconciliation to the ledger | IVC | Depends on volume |
| Review | Client review of the computation and the return before filing | Client and IVC | 1–3 working days |
| Filing | Submit through e-Filing or at the counter and retain the receipt | IVC | By the statutory deadline |
| Follow-up | Respond to any enquiry and archive the supporting file | IVC | As required |
| Scoping | Review the entity, period, filings due and current records | IVC | On enquiry |
| Document collection | Collect source documents, prior returns and statements | Client | 2–5 working days |
What to prepare
- Company affidavit, VAT certificate (PP.20) where issued, and the tax ID
- The accounting period and the filing deadline that applies to it
- Source documents: invoices, receipts, contracts and bank statements for the period
- Prior-period returns and the audited financial statements already filed
- Details of the authorised signatory and any e-Filing credentials in use
- For cross-border items: the counterparty's country and tax residence evidence
- A written authorisation where an agent files on the company's behalf
What "Can someone else act on your behalf for tax privileges for BOI-promoted companies, and what power of attorney is needed?" actually involves
This question sits within corporate income tax. The authority or standard that governs it directly is the Revenue Department, and the Board of Investment for promoted activities, and every case is assessed against the rules in force on the day of submission. IVC prepares the file, checks internal consistency and coordinates with the receiving office; we are not a government body and we never guarantee how an authority will decide.
Expenses without adequate evidence, or not incurred for the business, are added back regardless of how they were booked.
Loss carry-forward is limited in time, so expiring losses should be identified before the computation is finalised.
A materially low half-year estimate can attract a surcharge, so the PND.51 estimate should be supported by a documented calculation.
Rules and requirements to settle before you start
BOI privileges apply only to the promoted activity and require separate revenue and cost tracking from non-promoted business.
The tax computation must reconcile to the audited financial statements filed with the DBD.
Input and output VAT reports must reconcile to the return and to the general ledger for the same period.
Certain input VAT is non-creditable by law regardless of documentation, notably entertainment expenses and specified vehicles.
The mistakes that cost the most time
The most expensive pattern is treating the deadline as the start of the work. Monthly VAT and withholding returns depend on documents that arrive from suppliers and customers, so a file assembled in the last three days is the file where a missing tax invoice becomes an irrecoverable input credit rather than a phone call.
The second is inconsistency between systems. The return, the input and output reports, the payroll register and the audited accounts are all read together on review, and a difference nobody can explain turns a routine desk check into a full enquiry covering earlier periods as well.
Why files are delayed or returned
- A half-year estimate that cannot be supported by a calculation
- Expenses claimed without adequate evidence
- Promoted and non-promoted revenue mixed in one set of records
- A tax computation that does not tie to the audited accounts
- Reports that do not reconcile to the filed return
- Input VAT claimed on non-creditable items
Key terms in corporate income tax
- Input / output VAT
- VAT paid on purchases and charged on sales; the difference is remitted or carried forward.
- Section 50 bis certificate
- The withholding tax certificate the payer issues to the payee at the time of payment.
- PND.50 / PND.51
- The annual and half-year corporate income tax returns.
- PP.30
- The monthly VAT return, filed whether or not the period had activity.
- Permanent establishment
- A taxable presence in a country as defined by the applicable treaty article.
- DBD e-Filing
- The Department of Business Development system for submitting financial statements.
- Certificate of residence
- Evidence from a tax authority that a person or company is resident there for treaty purposes.
Official sources
- The Revenue Department (Thailand) — Tax registration, returns and e-Filing
- Department of Business Development — Financial statement submission (e-Filing)
- Social Security Office (Thailand) — Employer registration and contributions
- Thailand Board of Investment — Investment promotion and tax privileges
- Electronic Transactions Development Agency — e-Tax Invoice and e-Receipt standards
Scope and limitations
IVC provides accounting, tax compliance and document services as a private firm. This page is general information, not a case-specific tax opinion, and it is not issued by the Revenue Department or any other authority. Rules and deadlines change, so confirm the position for your own period before acting. Fees are quoted after scoping — please contact our staff by phone, LINE or email.
Information as of August 2026
Other questions in this group
- What documents are required for the annual corporate income tax return (PND.50)?
- What is the step-by-step process for the annual corporate income tax return (PND.50)?
- How long does the annual corporate income tax return (PND.50) normally take?
- Which authority handles the annual corporate income tax return (PND.50)?
- What conditions must be met before the annual corporate income tax return (PND.50)?
- Why is the annual corporate income tax return (PND.50) most often rejected or returned?
- How far in advance should the annual corporate income tax return (PND.50) be arranged?
- Can someone else act on your behalf for the annual corporate income tax return (PND.50), and what power of attorney is needed?
- What is most commonly overlooked in the annual corporate income tax return (PND.50)?
- Does the annual corporate income tax return (PND.50) require additional translation or certification?
- What happens if a document for the annual corporate income tax return (PND.50) is lost or expired?
- How does the annual corporate income tax return (PND.50) differ for foreign nationals compared with Thai nationals?
Need an answer for your own case? Talk to our staff by phone, LINE or email.