I've recently worked on a task that took several weeks to complete. It was a very intensive work, and on several nights and mornings I had to do over time.
When I started working here, such thing happened before and I was paid for the over time. However, at some point they said there is no need for me to do over time because the project's structure stabilized, I should be able to finish within the normal hours and there is no budget to pay the extra hours.
Some time has passed and I was able to finish everything in normal working hours, but lately I had the above task for which I did a lot of over time. Because the work was so intensive and at that time I wasn't sure how much the situation was going to continue, I didn't take note of the overtime hours spent. Also, in the last few days they said the task took too much to finish, but there were several technical difficulties which were not foreseen in the initial estimation.
During this task I took a week of vacation(for which I'm not paid) and now I need to give the timesheet for the month. I don't know what would be best to do because I don't know if or how much time should I ask as overtime.