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1. Employee waited too long, forgot about the detail of the time entry, affecting the accuracy of the time entry, like what happened, when it happened, and how long it took. Since some of the very important KPIs like utilization and agreement profitability are heavily rely on an accurate time entry, the accuracy of those KPIs will be affected too.
2. If the clients or other employees need to figure out what happened to certain tickets, and the employee who did the job didn't put time entry at the time, it will create trouble for the clients and other employees to understand what happened and what needs to be done next. 

Here are some service manager and business owner talking about how bad it could be:

How bad is your MSP doing in the late time entries?

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