Many cases start with the taxman’s time-honoured information source: a tip-off. If you have names and contact details of suspected tax evaders, and information on the way they shield money from the authorities’ eyes, the Revenue Commissioners have an online “tax evasion report form” and also welcome reports from members of the public by post or by phone. The form allows you to upload documents, such as advertising leaflets from the alleged offenders, and requests informants to provide as many details as they can including those of any suspected accomplices and “the make, model, colour and registration number of any…