The finance tab of a project shows a summary of any fiscal events that have been applied to this, or any subsidiary project. Costs accrue for any project or task when activities are recorded against it, based on charges recorded in the activity records. Specific fiscal events are also accrued for credit, debits or costs, and can be compared against initial estimates.
Values percolate up through the project tree hierarchy so financial status can be reported on at any level. For example if the research and development department is set up as a project, with individual development projects below that, then the projects can be reviewed, and so can the department as a whole. This could be extended further by breaking down into product lines.
Project managers with appropriate permissions can amend finance values, however it is better to correct or amend the relevent project event activity records.