The Customs Department has asked Japanese car makers Toyota Motor Thailand (TMT) and Isuzu Motors (Thailand) to pay almost 13.5 billion baht total for understating taxes on imported auto parts.
Somchai Sujjapongse, director-general of the Customs Department, said officials found, Isuzu imported more car transmission parts from the Philippines under the Asean Industrial Cooperation (AICO) scheme than it was supposed to from 2000-02.
Isuzu then paid 754 million baht less in import duties and 52.8 million less in value-added tax (VAT) than it should have, he said.
Under the AICO deal, products imported from Asean members are subject to a mere 5% import duty.
Normal duty for products imported from elsewhere runs 42%.
The Customs Department's appeal committee has resolved that Isuzu should pay 1.79 billion baht, as it took interest, penalty fees and the shortfall in tax payments from importing auto parts with a different product specification into account.
The committee decided the Japanese car maker also imported auto parts with different specifications.
It has therefore asked the company to pay the normal tax rate of 42% instead of 5%.
The department has also repeatedly asked TMT to pay a total of 11.7 billion baht in retroactive taxes for misdeclaring 245 shipments of components used to produce 20,000 Prius cars from 2010-12.
Of the total, 7.61 billion baht was import duty, 2.02 billion excise tax, 217 million tax charged by the Interior Department and the rest VAT.
TMT earlier appealed the demand, saying the troubled hybrid cars' components were imported under the Japan-Thailand Economic Partnership Agreement.
Executives from both TMT and Isuzu were unavailable for comment.
In another development, Mr Somchai said the owners of 178 of the 227 luxury cars reported missing from bonded warehouses had paid proper tax.
Of the 49 missing luxury cars, owners of eight have been arrested, while the other 41 are being pursued by the authorities.
The department found 25 officials, 37 importers and seven bonded houses were involved in tax avoidance.