The Inland Revenue Board (IRB) will soon launch an income tax audit operation on professionals involving architects, lawyers and engineers, says IRB chief executive officer Datuk Sabin Samitah.

He said based on risk analysis, third-party information and Bank Negara Malaysia analysis, some of the professionals had never declared their income.

Sabin said the operation would probably kick off in September or October.

"I would like to advise these professionals to come forward now and make a voluntary declaration (of their income)," he told a press conference after attending the Merdeka Gathering 2017 here today.

On the target of RM127.7 billion tax collection this year, Sabin said it was achievable, but several restrictions, which include the announcement of one percent reduction in tax rate, could reduce the tax collection.

"Another restriction is in the petroleum tax collection. It is estimated that IRB will get RM8 billion from petroleum tax, but we only managed to get RM3 billion so far, and this is a challenge for us," he said.

Sabin said the IRB had managed to collect RM75.7 billion in taxes so far this year, which is an increase of 2.72 per cent compared to the same period last year.

When asked whether the IRB had purposely targetted the family of Tun Dr Mahahir Mohamad in tax investigation following reports on a raid on the former premier's son's firms, Sabin said the IRB had never practiced selective or politically-motivated investigation.

"There is no political interference. Any investigation or audit on any individual or firm is based on a detailed risk analysis by the IRB.

"When we investigate or audit, we will not just investigate a company or its director, but will also investigate the whole group of companies as being practiced in other countries," he said.

-- BERNAMA