The system master file defines the default accounts for various general ledger transactions. For instance, when you generate an invoice the default accounts receivable account is defined in the system master file. If you change the chart of accounts, you need to insure all of the required default accounts are correct.
Required default accounts should be modified after the chart of accounts is finalized.
To open the System Master File:
Select "Files"
Select "System Master"
The "System Master Screen" is displayed. Click the GL Accounts Tab.
Modify the required accounts now.
See the System Master Section for more details.