Note: This article applies to Classic billing.
Once your draft invoice has been created you can make adjustments to the invoice without affecting the underlying items (tasks, disbursements, purchases). If you delete the invoice then the underlying items will be released, and if you then re-create the invoice it will revert back to the sum of the underlying items and your changes to the draft invoice will be lost.
Note: Changes made to the invoice will NOT affect the underlying data (tasks, disbursements, etc).
The recommended way to make adjustments is to group the items under headings on the invoice. If you make a change to the heading total then this will be applied to the line-items under the heading in a pro-rata basis.