Can someone else act on your behalf for personal income tax for foreigners working in Thailand, and what power of attorney is needed?

How this case runs end to end

Determine residence by counting days, classify each income category, gather withholding certificates and allowance evidence, compute the liability with allowances and deductions, file PND.90 or PND.91 by the deadline, and keep evidence of any foreign tax credited.

Stage-by-stage timeline

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 personal income tax for foreigners working in Thailand, and what power of attorney is needed?" actually involves

This question sits within personal income tax for individuals and foreign nationals. The authority or standard that governs it directly is the Revenue Department, under the personal income tax provisions of the Revenue Code, 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.

Allowances and deductions must be evidenced; the deduction is disallowed on review where the supporting document is missing.

A double tax agreement can relieve double taxation but has to be applied with residence evidence rather than assumed.

Employment income for work performed in Thailand is taxable in Thailand even when it is paid into an overseas account.

Rules and requirements to settle before you start

Foreign-sourced income remitted by a Thai tax resident is assessed under the rules in force for the year concerned, so the remittance date matters.

Residence is decided by days present in the calendar year, not by visa type or work permit status.

A full-form tax invoice must carry the prescribed particulars; a missing item makes the input VAT non-creditable even when the payment is genuine.

A nil month still requires a PP.30 filing; skipping it creates a late-filing record rather than nothing at all.

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

• Residence assumed from visa status instead of counted in days
• Withholding certificates missing at filing time
• Deductions claimed without supporting evidence
• Foreign remittances documented after the fact rather than at the time
• Tax invoices missing a prescribed particular
• A refund claimed before the supporting trail is complete

Key terms in personal income tax for individuals and foreign nationals

Certificate of residence

Evidence from a tax authority that a person or company is resident there for treaty purposes.

Tax residence

Status arising from presence in Thailand for 180 days or more in a calendar year.

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.

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