fill out

Usage

Preferred in American English; British English says 'fill in'.

Separable

The object can go between the verb and the particle: turn the light off, or turn off the light. When the object is a pronoun it must go in the middle: turn it off, never turn off it.

Practise it

Add it to your daily practice or see every verb with up.

Further reading: fill out on Wiktionary (CC BY-SA).