For tax payments/postbar payments and EACT respectively, a standardised payment reference is necessary. For an unstructured "Verwendungszweck" 140 characters are valid, for a structured "Verwendungszweck" 35 characters.
Special rules for the "Verwendungszweck" for tax payments are available pdf here (53 KB) .
Special rules for the "Verwendungszweck" for postbar payments are availavble pdf here. (139 KB) EACT (European Association of Corporate Treasurers) elaborated a structure via which the 140 characters of the text being available in XML-format for SEPA-transactions may be used for detailed reconciliations of invoice. The structure for the "Verwendungszweck" of EACT is available pdf here. (145 KB)
In this case, STUZZA offers you a service which can automatically detect the payment reference.