Corporate Tax Filing: Step-by-Step Process

Ready to file your corporate tax? Here's the complete step-by-step process for Thai corporate income tax filing.

 

Step 1: Prepare Financial Statements

Close Your Books

• Finalize all transactions for the fiscal year
• Reconcile all accounts
• Ensure all invoices are recorded

 

Generate Statements

• Balance Sheet
• Income Statement
• Cash Flow Statement
• Notes to financials

 

Get Director Approval

• Review with company directors
• Obtain signatures
• Apply company seal

 

Step 2: Calculate Tax Liability

Determine Taxable Income

Gross Revenue
- Cost of Goods Sold
= Gross Profit
- Operating Expenses
- Allowable Deductions
= Net Profit (Taxable Income)

 

Apply Tax Rate

Standard companies:

• Net Profit × 20% = Tax Owed

SME companies:

• First 300K: 0%
• Next 2.7M: 10%
• Above 3M: 20%

BOI companies:

• Promoted activities: 0%
• Non-promoted: 20%

 

Subtract Prepayments

• Half-year estimated tax paid
• Withholding tax credits
• = Final tax due (or refund)

 

Step 3: Complete Tax Forms

Main Form: Por Ngor Dor 50

Section 1: Company Information

• Tax ID number
• Company name and address
• Fiscal year period

 

Section 2: Revenue

• Sales revenue
• Service revenue
• Other income
• Total revenue

 

Section 3: Expenses

• Cost of sales
• Salaries and wages
• Rent and utilities
• Depreciation
• Other expenses
• Total expenses

 

Section 4: Tax Calculation

• Net profit
• Add-backs (non-deductible expenses)
• Deductions (200% items, etc.)
• Taxable income
• Tax rate applied
• Tax liability

 

Section 5: Credits and Payments

• Half-year tax paid
• Withholding tax credits
• Net tax due/refund

 

Step 4: Gather Supporting Documents

Attach:

• Financial statements
• Withholding tax certificates
• VAT returns (if applicable)
• Deduction support (training, R&D)
• BOI reports (if applicable)

 

Step 5: Choose Filing Method

Option A: E-Filing (Recommended)

Advantages:

• File from anywhere
• Immediate confirmation
• Extended deadline (May 31 vs. 150 days)
• Faster processing

Requirements:

• Digital signature
• RD Smart Tax account
• Scanned supporting documents

 

Option B: Paper Filing

Process:

• Print completed forms
• Attach physical documents
• Submit at Revenue Department office
• Obtain receipt

Deadline: 150 days after fiscal year-end (no extension)

 

Step 6: Submit Filing

E-Filing Steps

1. Log in to RD Smart Tax portal
2. Select "Corporate Income Tax"
3. Upload completed Por Ngor Dor 50
4. Attach supporting documents (PDF)
5. Review and confirm
6. Submit electronically
7. Download confirmation receipt

 

Paper Filing Steps

1. Bring 2 copies of all documents
2. Go to Revenue Department office
3. Submit at corporate tax counter
4. Officer reviews for completeness
5. Receive stamped copy as receipt

 

Step 7: Make Tax Payment

If Tax is Due

Payment methods:

• Bank transfer to Revenue Department account
• Counter service at Revenue Department
• Online payment via RD portal

Deadline: Same as filing deadline

 

Payment Slip

• Form: Por Ngor Dor 01
• Shows: Tax amount, company details
• Keep receipt for records

 

If Refund is Due

• Revenue Department will review
• Refund processed in 60-90 days
• Direct deposit to company account

 

Step 8: Record Keeping

Keep for 5 Years

• Filed tax return (stamped copy)
• Financial statements
• All supporting documents
• Payment receipts
• Correspondence with Revenue Department

 

Common Filing Mistakes

Mistake 1: Missing Deadline

Penalty: 1.5% per month on unpaid tax

Solution: File early, don't wait until last day

 

Mistake 2: Incomplete Documentation

Result: Filing rejected, must resubmit

Solution: Use checklist, review before submission

 

Mistake 3: Calculation Errors

Result: Audit risk, penalties

Solution: Double-check all calculations, use accountant

 

Mistake 4: Not Claiming Deductions

Result: Overpay tax

Solution: Review all eligible deductions (200% items, etc.)

 

Timeline for Calendar Year Companies

| Date | Action | |------|--------| | Dec 31 | Fiscal year ends | | Jan-Feb | Prepare financial statements | | Mar | Finalize statements, calculate tax | | Apr | Complete tax forms | | May 1-31 | Submit filing (e-filing deadline) | | May 31 | Payment deadline |

 

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Related Service: Accounting & Tax Compliance — We handle your entire tax filing process.