Users are human, and as humans, they are plodding error-prone agents of change. If you are setting up master records (Cards) in Dynamics GP, you should be familiar with the ubiquitous concept of Class IDs.
Classes make it possible improve the speed and accuracy of data entry in Dynamics GP, where master records are concerned. Customer, Vendors, Items, Fixed Assets and Employee master records all make use of Class functionality.
Using Classes, you can create meaningful categories for Customers, Vendors, Items, Assets and Employees, and ensure these records are rapidly and accurately assigned the key information, like the correct terms, shipping methods, departments, posting accounts, depreciation methods, etc.
Whether or not you've already entered or imported the bulk of your master records, your team should take the time to review the information, which can be controlled at the Class level for each of the listed master records and create useful classes.
When a class is assigned to a master record and a value is changed at the class level, you have the option of rolling this change down to all the members of the class. So, classes provide the ability to mass-change data in the system.
If you have questions about classes, a good place to start would be to ask your partner. If, by some twist of fate you do not have a partner, I would strongly recommend finding one - they can help you maximize the potential of Dynamics GP.