I do not know what the design looks like.
But as you mention, there are 2 different options:
- Radio button behaviour (the users choose one tab and fill in the form on that tab)
- Check box behaviour (the users fill in a form and can choose to fill in the forms on the other tabs in addition)
The difference needs to be made clear with the styling and description of the tabs.
To quote the article of Luke W on Selection Dependent Inputs:
"While most users are familiar with the concept of navigation tabs on the Web, the manner in which they fill in Web forms frequently impairs the effectiveness of the section tabs approach. When completing a form, many users move from top to bottom and, as a result, often ignore horizontal options. There is also a lack of clarity about whether section tabs are mutually exclusive. Will I submit my selections on all three tabs with the form—or only the selections I made on the active tab?"
Users will 'forget' the other tabs (especially with long forms).
The users will get unsecure about submitting the form.
I would use tabbing carefully and test it with a few people. At least use it either as checkbox or radio button consistently in the whole form, don't mix them up.