HMRC and other organisations (such as insurance companies) are searching the internet for evidence relating to your lifestyle.
HMRC in particular is looking for evidence of expensive holidays, expensive cars and large engagement rings to name but a few - this behaviour is not new, but it is being used more effectively by HMRC.
Why are they doing this? The answer to that question is simple; they are looking at the tax return you submitted and assessing the cost of your lifestyle to see if the two marry up.
Gone are the days when they sat in cars outside your house or business premises and followed you (yes they used to do that and still do in extreme circumstances).
The rule is this: if it's on social media, expect HMRC to review it and assess its worth against your self-assessment return.
Tax dodgers who boast about their luxury holidays and spending sprees on social media risk being discovered by HM Revenue & Customs as a result of sophisticated new computer systems.