Pre operative expenses?

Can anyone explain me what pre operative expenses are?

How are they to be treated for accoutning purposes?

Capitalise or charge to revenue?

When should they same be done?

At the year end or commencement of commercial production.

In my auditor office, preoperative expenses were capitalised prior to the date when the first sale invoice is raised?

Is it right?

Can raw materials purchases also be capitalised as pre operative expenses?