The Revenue Department has issued letters to 500,000 e-commerce operators requiring them to enter the tax system and pay proper tax.
About 10% of them have yet to enter the formal tax system, director-general Prasong Poontaneat said yesterday.
Prasong: No free ride for e-commerce
He said the number of e-commerce operators had grown substantially, but some of them had never filed a tax return since their sales revenue remained lower than the minimum taxable personal income.
All operators must submit tax claims each year even if their revenue falls below the minimum threshold, Mr Prasong said, adding that officials from his department were tracking e-commerce operators' data and annual revenue.
Under the current personal income tax structure, income of up to 150,000 baht is tax-exempt, from 150,001 to 300,000 baht is taxed at a 5% rate, 300,001 to 500,000 baht at 10%, 500,001 to 750,000 baht at 15%, 750,001 to 1 million at 20%, more than 1 million up to 2 million at 25%, more than 2 million up to 4 million at 30%, and more than 4 million at 35%.
The Revenue Department earlier expected 90,000 e-commerce service providers would be drawn into the tax system this fiscal year running from Oct 1 to Sept 30, pointing to heavy fines as the reason.
Tax evaders face fines of 200% of the unpaid tax plus interest of 1.5% per month.
Last year e-commerce-related operators numbered 900,000 including 145,000 small enterprises, with a market value for the sector of 750 billion baht.
In a related development, the Revenue Department is trying to entice more antique and amulet traders into the tax system to enlarge the country's taxpayer base.
However, antique and amulet traders frequently exploit a legal loophole that waives tax for those who possess such items for non-commercial purposes.
Investigating these traders is difficult since it is largely a cash business.
The Revenue Department recently said it was "highly likely" it would miss its 1.965-trillion-baht tax collection target for fiscal 2015.
The target represents optimistic growth of 15%, more than double past years' average of 7% growth.