Ministry permanent secretary Areepong Phucha-um Thursday said the committee's initial probe findings had concluded several senior officials may be involved in the fraudulent value-added tax (VAT) refund scam.
Of the 18 suspects, four are officials holding positions of senior director and specialists at the C-9 level, while the rest are officials at the operational level, Mr Areepong said.
He said the ministry has set up a committee to launch a disciplinary investigation into the four C-9 officials, while the Revenue Department has been assigned to consider action against the other 14. Mr Areepong said the ministry will also expand the investigation to look at whether officials at higher levels are involved in the scam.
The investigation will cover the entire Finance Ministry organisation, Mr Areepong said.
He said the ministry will also review regulations relating to VAT refund requests by entrepreneurs to try to reduce the risk of fraudulent refunds being paid out.
The ministry approved a 2-billion-baht budget last year for the Revenue Department to put in place a cross-check system for tax refund requests, but it has not yet been implemented.
Finance Ministry inspector-general Prasit Suebchana, who chairs the inquiry committee, said the panel was set up by the finance permanent secretary.
However, the Revenue Department has failed to cooperate with the committee and was reluctant to provide the panel with information on the tax refund fraud, he said.
The committee has sent five letters asking the department to submit information on VAT refund requests by 65 companies, but the department sent back information on only 20 firms.
The Revenue Department claimed it could not provide the information for the other 45 companies because doing so could constitution a violation of Section 10 of the Revenue Code which prohibits taxpayers' information from being disclosed.
The inquiry panel and the Department of Special Investigation (DSI) have investigated the 20 companies and uncovered fraudulent tax refunds worth 1.13 billion baht in Samut Prakan province, and illegal tax refunds worth 3.2 billion baht in the Bang Rak area.
Mr Prasit said the tax refund fraud involves an organised network, with a conspiracy between state officials and private companies.
The DSI will pursue criminal action against the perpetrators while the Anti-Money Laundering Office will try to retrieve the money cheated through fraudulent refunds, Mr Prasit said.
He said the inquiry found that those involved in the VAT fraud would offer people 200-500 baht each to use their identification cards. They would then use those ID cards to set up companies.
People who let their ID cards be used in exchange for cash were mostly farmers and labourers in Phichit and Tak provinces, Mr Prasit said.
The gang then used the ID cards to register companies, open bank accounts and apply for VAT registration with the Revenue Department, he said.
Even though some were newly established companies, it appears officials processed the companies' tax refund requests very quickly, Mr Prasit noted.
He also said some companies set the prices of goods at hugely inflated rates, hoping to obtain higher refunds.
At the same time Thursday, Revenue Department director-general Sathit Rangkhasiri held a separate press conference to release the department's findings in the case, though the information differed from that of the finance permanent secretary.
Mr Sathit said his department has found 38 entrepreneurs suspected of being involved in the VAT refund scam.
The fraud had cost the state about 2.87 billion baht and there are 10 officials within the Revenue Department suspected of being involved, he said.
Mr Sathit said the department's inquiry had not yet turned up any corruption — it was only a case of the officials' "carelessness" in performing their duties.
The department will not launch disciplinary action against these officials, Mr Sathit said.