MODCHQ - SET UP AND MAINTENANCE Ó UNCTAD – SITE (V1.15) 10.16 A  predefined  rule  may  be  inserted  in  the  Commodity  Code  to  modify  the  normal  calculation  of duties and taxes. The rule could be defined to charge an excise duty or do a duty comparison to charge a higher or lower tax based on two different bases. A full explanation of rules, their syntax and use, is given in Appendix A. Fig. 10.13  MODCHQ : Functions: Database Management: Customs Tariff: Commodity Code: update Duty and Tax rates applicable to the commodity Code must be inserted using this screen. An actual rate can be inserted in the column or a General Note defined under the option previously explained in this section under Tariff components. Commodity Code management can also be undertaken using the  ‘Simplified Update’ Tariff option explained later in this document . Customs Procedure Customs Procedure Codes (CPC) is used to identify the Customs regimes to which are goods are being entered and from which they have been removed. The CPC signals to the system whether the declaration is for an import, an export, transit, or any other circumstance possible in a Customs environment.  The  Code  identifies  to  the  system  how  the  data  input  from  the  declaration  is  to  be handled and how the declaration is to be processed. The menu options under 'Customs Procedure' are: · Model of declaration; · General Customs Procedure; · Previous Procedure; · Requested Procedure; · Action; · Extended Procedure Code; · Additional Code; · Agreement; · Offences.