When viewing Reports in the Profit and Loss module, there are several view options. Click on the view options icon, then the pencil under Report Content. Tick the YTD box to see the accumulated WIP forecast from the beginning of the year until present. 

In the screenshot above, the accumulated WIP forecasts from January to March make up the year-to-date Live forecast for March. The year-to-date Live forecast for March will be added to the WIP forecast for April, to create April’s year-to-date Live forecast, and so on month by month.