There are a variety of questionnaire form options people use, such as Google Forms or and Qualtrics.  The three main aspects to accessible form questionnaires;

  • technical code behind the scenes, 
  • the actual content of the questions,
  • and the visual design.

Technical:

Optional form widgets are available for text, multiple-choice, and more.  Some of these form widgets are more accessible than others.  Below are links to some resources that explain which widgets have the potential to be accessible.  

Qualtrics:

Google Forms:

Content:

It is possible to use an accessible widget, but ask a question in a way that does not make sense.  An example would be, "Rate your opinion on a scale of 1 to 5". The problem with this is that there are no instructions indicating which is best. It is 1 best or is 5 best. 

All other WCAG rules apply, like ensuring links have descriptive names.

More info on accessible form content.

Visual:

Most questionnaires provide the option of choosing theme colors. Choose a theme that has easy to read text with a high contrast ratio.