Forum Discussion
Make a FIeld not required
Once you enable content types, the required option moves from the list field to the content type. You'll have to open the content type and edit the required/optional/hidden choice for that field in each content type separately.
To complicate matters here, is the fact that you're DO number looks to be the default Title field. The Title field is an important field and you need to be careful with it as it is the main identifying field and it does behave a little bit differently from other fields. Keep in mind that this is the field people will click to open the item form, so leaving it blank is not a good best practice.
It's fine to rename the Title field. I do it all the time. But the Title field is always required. If you need the DO number to be optional, I would either pick another field to use as the Title field or add a default value like "Enter DO number". That way there is always a value (which fulfills the requirement) and it's a static value so easy to filter or program around.