Hi, 
in Project Definition you find the tab “Margin”. In that tab IFS display the margin of the project so normaly you don’t need to register losses:
 

Additional to that it is possible to register cost with “report project cost” function:

 

There is a seperate posting contorl for that costs (PRJC3 and PRJC4), based on that you could set up an report code for losses and map it to respective account. 

regards Sebastian