Accountants have been warned to probe clients on their online trading activity. The warning comes as a result of Revenue & Customs investigating businesses using social media sites. The Revenue is increasingly monitoring the use of online trading activity in the form of social media and blogging sites as an extension of its practice to monitor small ads in local papers and online 'auction' sites such as Ebay. Former ICAEW Tax Faculty chairman and current chairman of the Tax Advice Network Mark Lee has warned accountants that the Revenue will be looking into their clients' online activities more closely. Lee has urged accountants to extend traditional questions they ask clients about new sources of income, in a bid to stop them overlooking online taxable activities. 'As a result of blogging or dabbling in social networks, clients could be generating income through affiliate links with Amazon, Google Adsense or other less well-known businesses that generate sales through affiliates,' he said. 'The point is to be aware that the Revenue are looking, or could be looking, and that they could check back later if they have reason to think a person has not been truthful,' Lee added.