Periodically, inside and outside counsel need to revise the budget for a matter, and the law department should then revise its matter management system to show the new budget figure. Unless there is an audit trail or the revised budget does not over-write the original budget, it will be impossible for the law department to calculate the original or subsequent accuracy of the law firm’s budgets.
Another approach is to calculate the difference between actual spend and budgeted spend each time the budget changes. That cumulative figure could be stored and analyzed. The best law firms would have the least total discrepancy between their budgets and their actuals (See my meta-post on budget entries, Nov. 7, 2005.).