The purpose of this paper is to analyse preferential features for a simplified tax regime (STR) in the view of two important players in its application: chartered accountants and tax auditors. Portuguese Chartered Accountants (PCA) have a key role in recommending the STR to small firms and in its accounting and fiscal monitoring. Tax auditors, working for the Portuguese Tax Authority, control the regime´s application, and are also important agents in the STR´s functioning. A questionnaire was used as primary data collection method. Out of the 435 questionnaires considered valid, 315 were answered by PCA and 120 by tax auditors. Preferences for the STR´s design are the use of presumptive or indirect methods, specifically when the computation of tax to be paid is made on the basis of turnover and activity sector. Respondents also venture that it should not be coordinated with the value added tax (VAT) cash accounting; it must be optional and keep in place mandatory certification by PCA.