Watch out if you buy and sell large numbers of items on the internet - the taxman may be after you soon.

HM Revenue & Customs (HMRC) is planning to target an increasing number of sole traders and small companies across the South East who do business online.

This latest campaign will focus on individuals such as private tutors and coaches, including fitness instructors, and people who buy and sell items as a trade on the internet, alongside tradesmen with a turnover above £73,000 who are not yet VAT registered.

Err on the side of caution or you could end up in court, says Kevin Hall, tax investigations director at accountants Baker Tilly in Kent.

"There are many people who buy and sell small numbers of items on the internet who won't be affected by HMRCs latest campaign. However, it is important that those who are making a living out of the practice, and those who sell more than a few items a year, are fully aware of the tax implications and obligations that they are subject to.

"The same applies to individuals who are earning a living as tutors or a coach, whether this is their main career or to supplement another job - tax and NIC are often overlooked, and HMRC knows.

"Unfortunately, for the many small businesses and sole traders at risk from this new campaign, ignorance is no form of defence, and the consequences could not only be costly, but in some cases will lead to criminal charges and convictions. HMRC is known to be looking actively for many more prosecutions of tax cheats."

The latest in a number of recent efforts made by HMRC to catch individuals and businesses evading tax include using technology, such as "web robot" software, which searches the internet to find information on specified people and companies.