When you define the element link you can define how the element values are costed for the group of assignments defined by the link criteria. For example, you may want to cost the same element to different codes for different payrolls.
You can enter Costing information at the element link level if you have set up a segment of the Cost Allocation flexfield with the qualifier Element set to Yes. If you set the qualifier Balancing to Yes, you can do double entry accounting.
The values you enter at the level of the element link apply, by default, to all entries of the element for all assignments matching the link. However, you can set up cost allocation so that users can override the account codes for one assignment, or for a single entry, if required. For example, with timecard entries you may want to record different cost centers for different hours worked. In this case you would want to enter the cost center information when you enter the timecard element.
You enable this by setting up a Cost Center segment with the qualifier Element Entry set to Yes.