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Corporate Tax Filing: Procedures, Required Documents, and Filing Channels

  • Writer: Thanuwat Khumkainam
    Thanuwat Khumkainam
  • Jun 8
  • 5 min read

Updated: Jun 9

Corporate Tax Filing refers to the submission of corporate income tax returns by companies, partnerships, or legally recognized organizations. It is divided into two main periods:

  1. Mid-year Tax (Form PND.51)

  2. Annual Tax (Form PND.50)

Currently, the Revenue Department encourages taxpayers to file their returns via the online system (e-Filing) to enhance convenience, speed, and reduce paper usage. Therefore, taxpayers should prepare all necessary documents and information in advance before submitting through the e-Filing system.


Corporate Tax Filing: Procedures, Required Documents, and Filing Channels
Corporate Tax Filing: Procedures, Required Documents, and Filing Channels

Required Documents and Information for Corporate Tax Filing


Before submitting tax returns, it is essential to gather accounting data and important documents, including:

  • Financial Statements – such as the profit and loss statement, balance sheet, and cash flow statement, preferably audited (if applicable).

  • Accounting Records – including income and expense ledgers, journals, general ledgers, receipts and payment vouchers, and withholding tax certificates (if any).

  • Auditor’s Report – a financial statement certification letter, required for companies legally obligated to undergo an audit.

  • Shareholder List (Form BorJor.5) – an up-to-date list of shareholders or partners.

  • Other Supporting Documents – such as capital certificates, asset listings, depreciation schedules, and tax computation worksheets (reconciling book figures to taxable income), etc.


Corporate Tax Filing ProcessThe process can be summarized into the following key steps


  1. Prepare Accounts and Estimate Net ProfitPrepare complete accounting records, including income, expenses, and financial statements, to calculate the net taxable profit for each period.

  2. File Mid-Year Tax Return (Form PND.51)For the first half of the accounting year, submit Form PND.51 within 2 months after the end of the first 6 months.For example, if the period ends on June 30, the filing deadline is August 31 (with an additional 8-day extension for online filing).

  3. Pay Mid-Year TaxPay the preliminary tax based on estimated mid-year profit. At least 50% of the estimated annual tax must be paid in the mid-year filing (PND.51).

  4. Prepare Year-End Financial StatementsAt the end of the accounting period, prepare the final financial statements (profit and loss, balance sheet, etc.) to be audited (if required) and calculate the remaining tax due.

  5. File Annual Tax Return (Form PND.50)Submit Form PND.50 within 150 days from the end of the accounting period.For companies using the calendar year (ending December 31), the deadline is May 30 (or 158 days if filing online).

  6. Pay Annual TaxPay the tax due as calculated in Form PND.50 within the deadline. Payment can be made through banks or via the online system.


Note: Filing tax returns via the online system (e-Filing) allows for an 8-day extension beyond the standard filing deadline.

Steps for Filing Form PND.50 via the e-Filing System


  1. Log in to the SystemUse your registered username and password to log in to the e-Filing portal. Navigate to the menu “Online Filing”.

  2. Select Form PND.50Choose Corporate Income Tax Return (Form PND.50), which is the designated form for filing annual corporate tax returns.

  3. Fill in the FormEnter general information such as the tax year, accounting period, income details, and deductible items. The system will automatically calculate the tax payable, including any applicable surcharge or penalty.

  4. Upload Financial StatementsAttach PDF files of the financial statements and supporting documents as required in the form (e.g., balance sheet, profit and loss statement). These documents support the tax calculation.

  5. Review and Confirm SubmissionCarefully review all entered data, then click “Confirm Submission.” The system will generate a Reference Number to confirm the successful filing.

  6. Pay the TaxAfter successful submission, go to the “Online Payment” menu to pay the corporate income tax. Payment can be made via the Revenue Department’s E-Payment system, through participating banks or internet banking services.(Note: You may choose to pay taxes for both Form PND.50 and PND.51 together in one transaction.)


Steps for Filing Form PND.51 via the e-Filing System


  1. Log in to the SystemFollow the same login process as for Form PND.50 using your username and password, then go to the “Online Filing” menu.

  2. Select Form PND.51In the online filing menu, choose Mid-Year Corporate Income Tax Return (Form PND.51).

  3. Fill in the FormEnter mid-year financial data, such as half-year profit ratio, deductible expenses, and other required information as specified in the form.

  4. Confirm and Submit the FormReview all entered information and click “Confirm Submission.” The system will calculate the estimated tax payable and generate a Reference Number to confirm submission.

  5. Pay the TaxPay the tax amount as calculated by the system.(Note: You may choose to pay this tax together with the payment for Form PND.50, as previously mentioned.)


You can file tax returns and make payments for all types of tax forms at the following link:

(This is the official e-Filing portal of the Revenue Department of Thailand.)


Penalties and Corrections for Tax Filing Errors or Late Submission


  1. Fines and Surcharges:

    • If there is tax due and the filing is late, the taxpayer must pay a criminal fine of up to 2,000 THB and a surcharge of 1.5% per month on the unpaid tax amount.

    • For example:

      • Filing late within 7 days: fine of 1,000 THB

      • Filing late more than 7 days: fine of 2,000 THB plus surcharge of 1.5% per month on the tax owed

    • If the filing is late but no tax is owed, the taxpayer pays only the fine (up to 2,000 THB) without any surcharge.

  2. Correction of Returns (Amended Filing):

    • If the wrong form was submitted (e.g., filed late or used the incorrect type), taxpayers can file an amended return to correct the error.

    • Taxpayers should prepare an additional or corrected tax form and submit it to the Revenue Department with an explanation of the mistake.

    • If the amended return is filed within the deadline, no criminal fine is imposed.

    • If filed after the deadline, a surcharge of 1.5% per month on the additional tax payable applies.

  3. Example:

    • If a taxpayer forgets to file or files the wrong form (e.g., files Form PND.90 instead of PND.50), they should prepare a corrected form and contact their local Revenue Office to submit the corrected filing.

    • They must also pay any due taxes, fines, and surcharges as required by law.


Filing corporate income tax requires careful attention at every step — from accurate bookkeeping and thorough document preparation to choosing the appropriate filing channel (Revenue Office or online). This helps prevent errors and penalties.

Generally, Form PND.51 (mid-year) must be filed within 2 months after the end of the first half of the accounting period, while Form PND.50 (annual) must be filed within 150 days after the end of the accounting period.

If you file late or submit the wrong form, promptly correct the mistake by submitting an amended return and contacting the Revenue Department as soon as possible to avoid potential fines and surcharges.



Let iACC Professional handle your business tax filings with confidence.

If you’re a business owner or corporate executive seeking accurate and lawful submission of both Form PND.50 and PND.51, reducing risks of fines or back taxes, trust us to support you.

Ensure correctness, transparency, and timely filing — make iACC Professional your tax partner today!


Phone: 086-345-0265


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