See Section 381-90 TCA 97 make up you mind based on this-loss incurred in a year of assessment may be deducted from any other income chargable to tax in that year
I let others make up their own mind on interparation of it.
I would only offset on a case by case basis even if losses avaiable.
S.381(1)TCA1997 ,the ROS offline application , Line 114 of the 2008 Form 11 (www.revenue.ie/en/tax/it/forms/form11.pdf ) and the 2 Notices of Assessment with such claims on desk as I type, would all appear to disagree with you.
For Reference S.381(1)TCA 1997 states :-
"An individual who makes a loss in the course of his trade, profession or employment for a tax year is entitled to have his income from all sources reduced by the amount of the loss. "
S.382TCA1997 deals with carry forward which is of course correct and an alternative available to the trader.
Additionally there may be circumstances where carry forward is more beneficial than same year set-off. As Papervalue said, look at it on a case by case basis.