jQuery Validate Uncaught TypeError: Cannot call method 'getAttribute' of undefined

Question

Given this HTML using jQuery validate

  
  I accept the          


        

Answer 1

The 'name' attribute is missing:

<input id="accept-terms" name="accept-terms" type="checkbox" class="required"/> 

(This took me a while to figure out so I thought I'd share the question and solution)

Also: Check the comments below, as others have posted other causes for the same exception.