I work from home. We live in a rather small apartment so my work desk is actually part of the dinning room. In other words, I can't close the door and forget about it when done for the day.
Working from home is not an easy thing even without ADHD. Ask any 9-5 person who's made the transition. Distractions are all around, you have to manage your own time, and maybe have to deal with kids or a spouse who think that just because you are home, you are at their disposal.
One trick my pdoc showed me: Get to work as soon as you roll out of bed. Don't worry about getting dressed or doing your hair. Get coffee--straight to work. Work for about an hour and a half then take a short break. The idea here is to avoid letting your mind wander away from work tasks. He said that even on the short breaks, don't get involved in anything other than feeding yourself and going to the toilet.
It has worked well for me. He also suggested using a timer such as an egg timer to keep yourself on track.
Working from home can have great rewards especially if your like me; I don't care for the social aspect of working outside of the home. I just don't want to deal with the drama and crap that comes with it. But, you do have to find a way to be disciplined about it or it won't work. Either you won't get your work done and be let go or you will feel like your always at work because your trying to catch up.
Good luck to you and, I would try and clarify with the boss about time keeping and billing.