• The most common general types of purchasing contracts are the lump sum purchase agreement, the installment purchase agreement, the requirements contract, the output contract and the real estate sale and purchase agreement. Each of these types of purchasing contracts have their own special features.
  
  

Lump Sum Purchase Agreements

• A lump sum purchase agreement is an agreement in which the buyer purchases all products in a single installment, with full payment due either immediately or at a specified time after the agreement is signed. The products may be delivered in a single shipment or in a number of shipments over a period of time.
  
  

Installment Purchase Agreements

• An installment agreement is an agreement in which payment and delivery are made in periodic installments (1,000 widgets per month at $3 per widget, for example). In most cases, the parties will conclude an umbrella agreement that sets out terms that apply to every transaction, and then follow up with periodic purchase orders. The purchase orders become integral parts of the umbrella agreement as soon as they are issued by the buyer and accepted by the seller.
  
  

Requirements Contracts

• A requirements contract is a contract in which the seller agrees to provide the buyer with the purchaser's requirements for a certain product during the term of the contract. If interpreted literally, the buyer's "requirements" could be zero; however, courts have imposed a good-faith requirement that the amount of the buyer's purchases meet a reasonable minimum as anticipated at the time the contract was signed.
  
  

Output Contracts

• An output contract is a contract in which the buyer agrees to purchase all of the seller's output of a particular product during the term of the contract (the reverse of a requirements contract). Similar to the requirements contract, the seller's minimum output must be reasonable in light of general expectations present at the time the contract was signed.
  
  

Real Estate Purchase and Sale Agreements

• A real estate sale and purchase agreement is an agreement to sell real property. "Delivery" of real estate is perfected when the seller transfers marketable title to the buyer, as evidenced by the title deed at the closing. If either party unreasonably delays the closing, the other party may rescind the contract.