User is billing a fixed-type project, but the Net Bill is higher than its contract amount. How to ensure that the contract amount limit is not exceeded on a project?
The Net Bill value on the Create Batch Invoice screen is the sum of approved billable, but unbilled time and expenses logged on a project. Normally, when the total amount from time and expense entries that are part of the contract amount (non-extra entries) reaches the contract amount for a fixed-type project, Core changes any new non-extra entries to non-billable by default, provided there are no project rules set that cause Core to skip this evaluation against the contract amount.
However, you can always mark the new entries as billable manually or as Extra so that the evaluation against the contract amount is not triggered. These entries can cause the total billable amount on the project to exceed the contract amount. You can even change the Net Bill amount to a value that is higher or lower than the contract amount. To impose a stricter limit on the contract amount, you can use the project rule Prevent time and expense entry after reaching contract amount. Note that you can still create non-billable and extra entries when this rule is active as they are not considered part of the contract. It only prevents you from creating billable non-extra entries. Moreover, you can still change the Net Bill manually. Check the Core Help for details on the project rule.
Another option you might want to consider is creating a separate phase under a project just for reimbursables. After creating the separate phase, you can enter the expenses under this phase without affecting the contract amount previously set.