Contribution the liability will be represented by the profits of the current chargeable accounting period as diminished or increased by the payments. For Excess Profits Tax the liability will be computed by reference to the excess (if any) of the profits of the current chargeable accounting period, as diminished or increased by the pay- ments, over the basic standard enjoyed by the concern. 3. Where works have been closed down, the scheme provides that the machinery should be kept intact and ready for use unless the factory premises are requisitioned by the Government.