I've got a long term client that I'm currently on a 15hr a week arrangement with for a flat monthly rate with the general understanding of about 3hrs a day, with flexibility on managing that. Since it is a long term respected client, and a guaranteed rate, I'll sometimes go beyond the time to get certain things done, but am diligent about meeting the minimum otherwise. He manages what I work on daily using a bug tracking system for the project, assigning and checking things on completion, and there is daily interactions 90% of the time, unless he is away for business.
Each month I invoice him for the month and the flat fee, and have for 5 months now. This month after invoicing him he asked for a detailed itemization on where the time was spent and the dates of completion for each item, so he can "know where his money is going". It was a slower month due to him being away on business some.
My question is, what responsibility is it for me to provide a post-month itemization if we are not on a task or project based arrangement and it has never been my responsibility to manage or provide this? Basically, it is pretty tedious to have to figure this out post-month, when all I track is the 3 hrs a day gets met. Should the time invoice be enough for a client?