What is credit transfer (also known as "transferability"), and who can use it?

Transferability allows taxpayers who earn certain clean energy tax credits to sell some or all of those credits to an unrelated third party for cash. The buyer and seller negotiate the terms and price of the sale. Here, the seller is the entity selling the credits, and the buyer is the one purchasing them. 

Note: However, applicable entities cannot use transferability. They can only use elective pay.