I guess you have checked the guides as well -
Submit Options
Specifies whether to merge the cost plan you are submitting with the approved budget, or to completely replace it.
Note: This option is hidden if you submit the first cost plan for approval. The option is set to Replace and is read-only if the grouping attributes or time periods are different from the attributes in the approved budget.
How to Create a Budget Revision
An approved cost plan becomes the budget plan for an investment. Because elements of an investment change, you can revise various parts of the budget, or can replace the budget entirely.
You can make two types of revisions to an approved budget plan:
Merged Budget Plan Revision
■ Submit a cost plan with new line items and merge the changes with the existing budget plan.
■ Submit a portion of a cost plan by varying the start and end dates for the submission, or update the field values in specific time periods. You can submit only the changed time periods and can merge them with the budget.
Replacement Budget Plan Revision
■ Submit a cost plan with deleted line items and replace the budget to remove those line items from the budget plan.
■ Create a cost plan, using different grouping attributes or time period types, and replace the budget.
Both revision types provide approval history. However, the replace feature enables you to delete line items that are no longer needed, and to revise grouping attributes and fiscal time periods.
When you submit a cost plan that revises an existing budget, you specify whether to merge or replace using the Submit Options pull-down list. This field appears only when there is at least one approved budget. If the new cost plan has a different structure than the existing budget, Replace is the only option.
NJ