STATE governments that are keeping a vigilant eye on the money flows and the evasions have found a new target: computer programs that enable businesses to keep two sets of books simply by plugging a flash drive into their cash registers.The software known as the tax-zapper software enables businesses, especially those that deal mostly in cash, underreport taxable sales and pocket money entitled to the government.Five states - Florida, Georgia, Maine, Utah and West Virginia - have enacted laws cracking down on the programs, and about a dozen others are considering similar proposals. If experts are to be believed, states are losing billions of dollars thanks to the software.

The software, which sells for around $500, can be installed directly in registers or through small memory devices that plug into them.The programs are most likely to be found in businesses such as restaurants, where cash volumes are heavy, because transactions using credit or debit cards leave a paper trail. Even by nipping off just a few of the actual sales per day, businesses can reap a considerable illegal reward over time.