The Hawai'i Department of Taxation is kicking off informational briefings next week on a new law intended to help collect an estimated $1 billion in taxes that go unreported and unpaid because they are part of cash transactions.

The department said it will be going out to businesses to inform them of a new law that broadens the powers of investigators, who will be able to inspect books, records and business premises when a court issues a warrant or writ of entry.

The department has been stepping up efforts to collect unpaid taxes, including running its first tax amnesty day this year along with debuting a Web site identifying Hawai'i's biggest tax scofflaws.

In testimony before the state Legislature, the department estimated $2 billion of taxes locally go unreported and unpaid, half of which is attributed to the so-called cash economy in which unrecorded and unreported cash transactions escape taxation.

Such transactions can include contractors who ask to be paid in cash, or businesses that substantially deal on a cash basis and fail to report accurate amounts for tax purposes.

The Legislature passed, and Gov. Linda Lingle signed into law, the Cash Economy Enforcement Act of 2009, saying increasing compliance is a priority because those who diligently pay their taxes are shortchanged by those who don't pay their fair share. Increasing compliance may help avoid future tax increases.

The new act includes:

• Establishing a new special enforcement section that can issue citations as well as cease and desist notifications.

• Fines for failing to produce licenses, permits, books or records.

• Fines for conducting more than 10 transactions per day in cash and not providing a receipt or record of the dealings.

• Fines for businesses that offer a lower price if the transaction is paid for in cash if no legitimate business purpose is linked to the different pricing.

• Fines for interfering with investigators or other department personnel trying to obtain information. People who threaten or use violence against investigators can be charged with a felony and face a fine.