The governing documents (for example, Articles of Incorporation and Bylaws) of your closely-held company may include provisions dictating to whom you may transfer your shares. Often, but not always, charitable entities are permissible shareholders, but you want to be sure. In addition, other shareholders may be given a "right of first refusal," which means that you won't be able to give your shares to William & Mary until all other shareholders have declined to purchase your shares. Be sure to review the governing documents for any requirements you need to meet before initiating the transfer.
Because we are a charitable entity, we must perform "due diligence" to ensure that accepting the shares won't jeopardize our charitable status or expose William & Mary to unexpected liability. We'll need to review the company's governing documents and talk with you and the company about any liabilities that may accrue, so please discuss your plans with us well in advance of the transfer.
Be careful. If you're already far along the process of negotiating a sale of your shares, the IRS may view your contribution of the shares to us as a "step transaction" by treating your contribution as if you had already sold the shares and contributed cash to William & Mary. If the IRS recharacterizes the transaction that way, you'll have to pay capital gains tax on the transfer. You'll still get a tax deduction for your contribution of cash, though, and William & Mary will benefit greatly from your gift. Note also that William & Mary cannot accept shares that it's required to hold or sell.