fill in, fill out

Jaka jest roznica pomiedzy fill in i fill out?
Mam 2 zdania gdzie w jednym bylo fill in - wypelnic aplikacje,
a w drugim fill out - wypelnic kwestionariusz.
I zastanawiam sie jaka jest roznica pomiedzy tymi zwrotami.

wersja z out jest amerykanska

lepsze slowo to ...'complete'..

First of all, disregard both posts above.
You fill out an application/questionnaire by filling in or supplying missing information.
When you have filled in all the blanks (or answered all the questions), you have filled out or completed the application.
Completing in not a better word for filling out.

gab-
my 'complete' is used when someone asks you to 'fill out' the form and they say'...please complete the application form, this form etc'..(don't say you've never come across that expression).