Some people believe that a contract exists only if there is a written document signed by both parties. This is not always the case. There are situations when verbal agreements can be binding.
Signed documents are a common form of contract (and are mandatory in some situations) but that is not the only form they can take.
In very broad terms, in order to form a contract you need:
Offer
Acceptance
Consideration
Typically, a contract is formed when:
"A" makes an offer.
"B" accepts the offer (after negotiation or without negotiation).
"Consideration" - something of value - is given by one party to the other party. This can be money, merchandise, labor, or "something else." 1
Example:
I offer to sell you my pen for $1.00 and you agree to pay me $1.00 for my pen. We have a contract.
Simple:
Our agreement has scope ("this pen") a price ("$1.00") and consideration (the value of the pen and the
value of the dollar.
It is a completed contract when we trade my pen for your dollar.
Not So Simple:
You need my pen today, but don't have cash on you. I give you the pen, you promise to pay me tomorrow.
You need my pen today, and have a dime in your pocket. I agree to take your dime as down payment/consideration and your promise of paying me $0.90 tomorrow, and give you pen.
You give me your dollar, but I need my pen for the rest of the day and promise to give it to you tomorrow
It is a completed contract when I have all of your dollar and you have my pen.
If you don't have my pen, or if I don't have all of your dollar, the contract is incomplete. There is potential for controversy - which probably means expensive attorneys.
It is pretty common for the terms of a deal to grow fuzzy in memory - even one as simple as the above example of an overnight transaction.
That's why industrial democracies and republics consume so much paper.
1
"Consideration" - the "third leg" of the contract tripod - is loosely defined as giving and accepting something of value. The giving and accepting of consideration marks a point in time where both parties agree-to-agree.
Consideration can be payment in full, a partial down payment or.... "something else."
It's the "something else" where things can get tricky.
A purchase order, a signature on a bid or making a down payment... not controversial very often. A handshake, ordering supplies, scheduling time to be on the job... not so clear.
In the "not so simple" examples above, handing off the merchandise with no payment or making a partial payment with promise of more is "consideration."
My lawyerly advice: Don't guess and don't take chances. Always get the consideration on paper and never misplace it, just like the contract itself.