Forvis Mazars Payroll Flash News - March 2026

On 2 March 2026, the Royal Gazette published a Royal Decree introducing a personal income tax relief measure in respect of expenses incurred for the purchase and installation of solar cell rooftop systems. The taxpayers may claim a personal income tax deduction for actual expenses incurred , capped at THB 200,000.

Conditions for eligibility

Qualifying Period

The purchase, installation, and connection to the electricity grid must be completed between 3 March 2026 and 31 December 2028.

The tax relief may be claimed only in the tax year in which the grid connection is successfully completed. 

For example, where installation commences in December 2026, but the grid connection is completed in January 2027, the tax relief shall be claimable in the 2027 tax year only.

Entitlement limitation

Each taxpayer is entitled to claim relief for one electricity meter and one solar rooftop system only.

The following must be registered under the same individual:

• Purchaser and installation service recipient (as stated in the e-tax invoice)
• Electricity meter owner
• Applicant for grid connection

The electricity meter must be classified as Type 1 (residential use).

The inclusion of a battery system is optional and does not affect eligibility.

Expenses claimed under this Royal Decree must not be used to claim tax exemptions under any other Royal Decree or Ministerial Regulation, in whole or in part.

System requirements

• The solar system must be an on-grid system.
• The total installed capacity per residence must not exceed 10 kWp.
• The tax relief applies to new installations only.

Illustrative scenarios

• A house with no existing solar system may install up to 10 kWp and claim the deduction up to THB 200,000.
• Where an existing system of 3 kWp is in place, an additional 7 kWp may be installed and claimed.
• In the case of multiple residences:
• A first house already installed with 10 kWp is not eligible for further relief.
• Another house with 5 kWp installed may be expanded by 5 kWp, and such additional installation qualifies for relief.
• Where the total installed capacity exceeds 10 kWp (e.g. from 3 kWp to 13 kWp), no tax relief shall be granted.
• Where a house already has the solar system, the installation of a battery only does not qualify for relief.

Required supporting documentation

• Copy of the taxpayer’s Thai national identification card
• Full electronic tax invoice (e-tax invoice)
• Application for connection to the electricity grid
• Approval/authorisation for grid connection

Source (in Thai):
Royal Gazette – Personal income tax allowance for solar rooftop installation