I have a client where I check emails and also her voice mails daily. I use TimeSlips, so I am able to turn on a time clock as soon as I pick up the phone or log into the email server. If there are no messages, l log out and stop the time clock. When I log in and check messages later, I start the time clock where I left off the last time. If there are no messages the two other times your total time will more than likely be less than 15 minutes. So, I charge the 15 minutes for the day. I've been doing this for over a year, and I think it is fair.

However, if the time clock says it took 18 minutes to check three times a day, then I round that up another 15 minutes, for a total of 30 minutes billable to the client.

I also have my sub-VAs use MyHours. There is no start and stop time clock feature (that I'm aware of), but it is a great FREE service and you might want to start out with it. You can also invoice your clients through MyHours, too.