I set up a test company exactly as a copy of the real actual company.
I have calculated per day what income I should be getting and multiplied it with the number of working days in that specific month.
I also calculated the COGS per day and multiplied it with the number of working days in the same month.
I did all the transactions as the real company would have done it month by month for the budget period of the following year.
The when you do the reporting you just comparitive column to compare the months.
Maybe it is a lot of work, but it works for me and by doing it month by month I get to do it.