Meaning trap
get in
submit (formally)
to send or deliver something, especially a document or piece of work, so that it is received by a particular deadline or authority.

Don't mix these meanings
Same phrase, different job.
to send or deliver something, especially a document or piece of work, so that it is received by a particular deadline or authority.
'get in' also has the more basic meaning 'enter or arrive'; this is the advanced sense.
Hear it in context
Notice where the phrase sounds natural.
Please make sure you get your expense reports in by the end of the week.
Candidates must get their essays in no later than Friday to be considered for the competition.
Fix the pattern
One small grammar move makes it sound right.
Not: Did you get in it on time?
Say: Did you get it in on time?
With a pronoun, the object goes in the middle: 'get it in'.
Which sounds natural?
Tap the one a native speaker would say.
'Get something in' is the natural verb for meeting a submission deadline; the formal version is a portal notice.
Build natural chunks
Words that usually travel with it.
get + submission + in
- your application
- the form
- on time
- by the deadline
Don't confuse it
Related
Other meanings and phrases to compare.
- get in (enter or arrive) — 'get in' also has the more basic meaning 'enter or arrive'; this is the advanced sense.