It does not have to be a 500 page legal contract, signed under seal and notarized but both parties in a consultancy agreement need a contract. Without a contract it is like playing solitaire with the four kings missing. You may play the game all the way to the end, but you will never win. 

Amongst the most important elements of the contract are:

• Expectations of services and deliverables (“the what”) and the specific criteria that makes them acceptable
• The definition of processes, methods, communication, standards and people (“the how”)
• Expectations of what the client must do  or not do to enable your success
• What you both will do if things change (“the what if”)

You can write it on a napkin, put it in an email or spray paint it on a conference room wall, but it needs to be written. It needs to be written not to enforce payment of the fee but for the most important purpose; to ensure the consultant and the client both agree on what and how something is to be done from the start and what defines “done”.

The worst possible consulting contract  for a consultant or their client  is to have a consultant parachuted into an engagement with a previously negotiated agreement; an agreement where the services are fuzzy, the deliverables are fuzzy, the expectations are crystal clear to everyone, and everyone has a different “crystal clear” vision.

If you are hiring a consultant into an existing engagement or you are a consultant coming onto one, take the time to review and re-align on the contact. It will make sure that you are playing with a full deck and  both parties can win.