I'd pass this KB along to my customer who was on Sage 100 Job Cost --- but they got sick of these type of errors and migrated away two years ago. This is an oldie but a goody.
Sage 100
Description
The Revised Contract amount in Job Masterfile Maintenance is incorrect after adding Change Orders.
Disclaimer
Backup Warning
Use caution when working with the below product functionality. Always create a backup of your data before proceeding with advanced solutions. If necessary, seek the assistance of a qualified Sage Business Partner, network administrator, or Sage Customer Support Analyst.
Resolution
If a change order entered for a job is not reflected in the Revised Contract field on the Job Status tab in Job Cost, Main, Job Masterfile Maintenance, a manual correction can be made to the data file.
Open Library Master, Utilities, Data File Display and Maintenance
Browse to ..\MAS90\MAS_xxx\JCxxx\JC1xxx.soa (xxx=company code)
In the Key field type the Job No.
Click Edit button
Select Field 8 (Revised Contract) and in the Change type the correct amount
Click Accept button