I do the same thing when I have to travel to customers' sites. I don't bill for travel days, and bill a uniform 8 hours a day for onsite.
That said, I live 2.25 hours away from the Phoenix Airport (up in the mountains) and I try very hard to not travel. When I work at home I use desktop timer and keep track to the minute. This is actually a low overhead activity.
A tip: documenting work tasks for invoicing is a high overhead activity. I reduce this overhead by attaching my complete working notes log to my invoices, and nothing else. I need copious notes on my work for technical reasons, and reusing my work notes saves me a lot of effort. I have the occasional client who doesn't like this because it is way too much detail for them, and in that case I charge them for the few minutes a day to write a short summary.
That said, I live 2.25 hours away from the Phoenix Airport (up in the mountains) and I try very hard to not travel. When I work at home I use desktop timer and keep track to the minute. This is actually a low overhead activity.
A tip: documenting work tasks for invoicing is a high overhead activity. I reduce this overhead by attaching my complete working notes log to my invoices, and nothing else. I need copious notes on my work for technical reasons, and reusing my work notes saves me a lot of effort. I have the occasional client who doesn't like this because it is way too much detail for them, and in that case I charge them for the few minutes a day to write a short summary.