A shelf financing refers to the  regulatory paper work required for a potential future capital raise. These documents are prepared in advance  once there has been shareholder approval for potential financings. This is done to speed up transactions once the decision is made in the future to proceed.

The documents lie dormant until some future time when they are pulled "off the shelf" by the CFO and put to use via a fresh capital raise. At the time,  dealers and banks will be engaged to determine what can be raised and at what price.