WIP can only be written off on a matter by matter basis using the WOW posting type in General Postings, this is done as below:
From the Main Menu go into the General Postings.
Select WOW posting type.
Select NEW.
Put in the matter number required and select the allocation grid box.
Select the WIP lines you want to write off.
Select the Floppy Disk to save.
If you have various matters do all of the postings and save first.
When you have completed all the matters select POST.
NB
WIP write off reversals can be done, you would follow the above but tick the box reversals to select what has already been written off.