Funding Deposits and Prepayments, can be logged against your Bill To Companies both Globally (so they can be drawn down from against any case file), and Case Specific.

A prepayment can be added to a company, via the Case List > Accounts tab where the company is a "Bill To" contact.

In this tab the current total value of any prepayments for the company will be displayed in the "Global Prepayment" field:

To view what deposits/prepayments this value is made up from, and to add any new prepayments, click the Details button to the right of this field:

...which will open the Prepayments window:

In this window, this outlines the total of all deposits/prepayments made by the company that can be applied to this case.

To add a new deposit/prepayment from the company, click the +New button at the top left of the window, and enter the payment details into New Prepayment box that appears:

By default, the prepayment will be created as a "Global" prepayment that can be drawn down from on any case file where the company is the Bill To.

Should you wish to only have these prepaid funds made available for use on this specific case file, enable the For this Case check box prior to clicking Save:

To drawdown from prepaid funds and apply them to an invoice that has been raised on the case file against the Bill To Company, select the invoice in the Case List > Accounts Table and click the +Apply Credit button:

This will open the Apply Credit window, where you can select the amounts and prepayment(s) that you wish to draw the funds from, and set the Payment Date:

Upon clicking Save this will create a Payment record on the case, applying the funds selected to the invoice, and reducing the value drawn from the total prepayments from the Company.