Meaning trap
fill in
substitute for someone
to do someone else's job or take their place for a short time.
Don't mix these meanings
Same phrase, different job.
to do someone else's job or take their place for a short time.
Another meaning of 'fill in' is 'complete a form'; compare the examples to keep the meanings separate.
Hear it in context
Notice where the phrase sounds natural.
Sarah is sick today, so I'm going to fill in for her at the meeting.
Last year, I had to fill in for my manager when she was on holiday, which was a great learning experience.
Fix the pattern
One small grammar move makes it sound right.
Not: Can you fill in me on Friday?
Say: Can you fill in for me on Friday?
To cover someone, use 'fill in FOR them'. (Bare 'fill someone in' means update them with news.)
Which sounds natural?
Tap the one a native speaker would say.
'Fill in for' is the natural workplace phrase for covering; the formal version reads like a contract.
Build natural chunks
Words that usually travel with it.
fill in for + person
- for a colleague
- for the teacher
- at short notice
- today
Don't confuse it
Related
Other meanings and phrases to compare.
- fill in (complete a form) — Another meaning of 'fill in' is 'complete a form'; compare the examples to keep the meanings separate.