I recently decided to leave a position after 4 months, as it simply wasn't working out. I had a two month notice period in my contract and had found a new position already that I am eager to start. I thought that a two month notice for four months of work seems unnecessary, as I don't have a lot to handover. As such, when I handed my notice in, I had a discussion with my manager about reducing my notice period to a month. This was well received initially, on the condition that I don't treat this as a notice period and look to complete certain tasks.
Since that conversation, additional tasks have been added to my Trello board and the manager has demanded for these to be finished before I leave. They have taken the position that my leaving is conditional on finishing the tasks, and refuse to give me a leaving date in writing until we are at that point. This means that I can't provide a concrete start date to my new employer, and when I do finish the tasks, I will simply have the rug pulled out from under me and be told that I can leave when in reality I need to give my new employer at least a weeks notice that I will be starting on X date.
I have no confidence that more tasks won't be added before the provisional one month leaving date that I gave even if I do complete the current set, and whilst they were doing me a favour, it really feels unprofessional to not give a concrete date or have my leaving be conditional. I have had discussions requesting this, however my manager is the managing director of the company and HR in this company is essentially run by command, and won't look to uphold any accountability to me on my manager's part (which by law I suppose he doesn't have). I'm not sure how to handle the situation, as I want to be professional and complete all the work set, but also I need to be able to give my new employer a start date.