With the public demanding more than ever that something must be done about tax avoidance and evasion, this documentary reveals for the first time the methods HM Revenue & Customs uses to find out who is and isn't paying tax and how they target those individuals. Leading the charge is Duncan McCallum, a veteran customs officer who has tackled drug rings, smugglers and massive duty fraud, while new teams are also targeting offshore accounts that could secure the Government millions in unpaid tax.