And you can fill in a form because you're supplying missing information. Fill out is generally used when you tell someone to enter all the fields on a form of more than one field. Example: Please fill out this form. Fill out means to complete by supplying requested information.
In my experience (Aus) a prescription is filled out (sometimes abbreviated to filled) by a pharmacist when the medicine is dispensed. Forms are sometimes filled out, but more often filled in.
Is it "to fill a prescription" or "to fill out a prescription"?
If someone asks you to fill them in, meaning to brief or inform them about something, could it in any way be construed as an invitation for sex, as when a girl playfully says so in response to, "I ...
What is the difference between fulfill and fill? In the following example, do they have the same meaning? I'll fill the form tomorrow. I'll fulfill the form tomorrow.
word usage - Difference between "fulfill" and "fill" - English Language ...
When to use the former and the later? Example sentence: The brunch didn't fill me (up).
"Fill me" vs "fill me up." - English Language Learners Stack Exchange
With respect to the more common use of shortage - when used in conjunction with a commodity - rather than fill, one would be more likely to use the word satisfy, for example
Is it possible to use the verb "fill" with the word "shortage"?
In school, for exams we FILL UP forms. But I have seen people saying "FILL IN the form." Fill the form in OR fill the form up, which is correct. Please explain.