Reconstructing time from memory tends to lose the short, scattered work first - though we found no primary source that quantifies how much, so we do not publish a leakage rate. Put a number on it for your own firm instead: ten consultants billing at $225 per hour, each losing just two billable hours a week, is $234,000 of unrecovered revenue a year. Whatever your real leakage rate, the arithmetic is unforgiving.
The problem is compounded because the leak is invisible. Your invoices look complete. Your timesheets get submitted. But the hours that didn't get logged - the 20-minute client call on Thursday afternoon, the hour of research that happened outside the office - never appear. They're not disputed; they simply never existed in the system.
Beyond direct revenue loss, poor billable tracking also corrupts your project cost data. If hours aren't being logged accurately, you can't know whether a project is profitable. You can't compare your estimated cost to your actual cost. You can't see whether your utilization rate is healthy or declining. Every downstream metric depends on the accuracy of time logs.
The solution is not discipline - it's friction reduction. Consultants don't skip time logging because they're lazy; they skip it because logging time is inconvenient. The right timesheet software makes logging so easy that it happens naturally, as part of the work rather than after it.