The taxman is to use improved surveillance software to target online traders using marketplace websites but failing to pay tax.
HM Revenue and Customs (HMRC) has warned that its new campaign would try to identify regular sellers on eBay, Auto Trader, E-auctions, Amazon, Craigslist and Gumtree.
Occasional sellers of personal items do not need to pay tax, but people earning a living as self employed traders may need to pay income tax, national insurance and VAT.
HMRC said the data it gleaned would be compared with its existing computerised records for income tax paid under self-assessment or PAYE, tax credits and national insurance.
“It shines a light onto previously hidden relationships, uncovering anomalies between such elements as bank interest, property income and lifestyle indicators before homing in on unexplained inconsistencies,” an HMRC spokesman said.
The taxman is also planning to launch more disclosure campaigns in this current tax year, aimed at specific groups of individuals, such as private tutors and fitness coaches, and tradesmen.
In the past couple of years the authorities have been making special efforts to get doctors and dentists, plumbers, and more recently restaurateurs, to come clean and pay the right tax.
HMRC first used computer software four years ago to track down tax-dodging internet traders on eBay.
Tens of thousands of people are thought to make part or all of their living by selling goods on online market places.