Invoices should be batched once a month and submitted between the 1st and the 15th of each month. A master purchase agreement is a legally binding contract between buyer and seller, and typically relates to buying and selling goods rather than services.This Master Sales Agreement (the "Agreement") is entered into between the buyer listed on the applicable Purchase Order ("Buyer") and Calimetrix, LLC. Our firm advises and represents buyers, sellers, associations, and lenders in many Massachusetts cities, including Somerville, Brookline, and New Bedford. For a consultation, give us a call at 781-843-2200 or fill out our contact form online. Use our free payment plan agreement form to spell out all the terms and conditions of a loan if you need to establish a payment schedule with someone.