I am using master planning & forecasting.
I give forecast for year.I use forecast reduction principle as "Purchase/sales orders".
As per AX-Help if I use this reduction principle then forecast should be reduced by the sales order quantity.
But I can not see any reduction in the sales forecast in Net Requirements.
Following are the screenshots for elaborating:
I presume your coverage code reduction key is blank. Set something in it (100% a month say) and run again.
What Coverage Group were you using?