The technical assistance was led by three European experts: Rafael Peláez Carazo, of the National Office of Fraud Investigation (ONIF) of the Spanish Tax Agency (AEAT); and Elza Maria Sequeira and Nuno Alves Paulo, of the Portuguese Tax and Customs Authority.

The issuing of invoices in sales operations in Colombia is a formal obligation which is mandatory for taxpayers. The legal requirements for invoices are especially useful for the Colombian tax agency (DIAN) for control of taxable bases linked to sales taxes. The allowable invoicing systems affect the receipts issued by the electronic cash registers used by taxpayers that offer a wide variety of goods for sale (chain stores, supermarkets). The special characteristics of these invoicing systems require a certain amount of training and specialised knowledge on the part of tax auditors to detect deletions and tampering with the transaction records in these invoicing systems.

In this context, the activity was aimed at transmitting to the civil servants of the DIAN the techniques and solutions adopted to combat fraud by the issuers of invoices in Europe, with special emphasis on the Portuguese and Spanish experiences. Special attention was devoted to the auditing regulation and procedures applicable to revenue control to prevent electronic suppression or evasion of sales tax through cash registers.

This activity is part of the European Union's EUROsociAL cooperation programme in the "Promotion of voluntary compliance with tax obligations" action of the Public Finance area, in which the Spanish State Tax Agency (AEAT) is acting as the operational partner.