If you already have the file number, you should send the PCC, it will save you a little bit of time.
Just be sure to include all the relevant info when you will be sending it.
Something like:
Hello my name is XXXX
Date of Birth: XXXXX
Application # : XXXXXXX
Here I submit the Police Certificate (PCC) for XXXXX country, as I hadn't had a chance to submit it along with the application.
Please kindly attach it to my application,
best regards
XXXXX
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this should be enough. You won't be getting a confirmation from CIC in most cases.
I did send mine with registered post, so I knew when they were delivered.
After many email (3 or 4) asking CIC to confirm that they received the PCCs they confirmed, but don't count on it. Surely people on the phone will not tell you that.
Also, you might order GCMS notes sometime down the road just to see how your case is doing, and there you will find a record on all the incoming and outgoing communications with you. So something like a PCC you submit will be regarded as an ingoing communication in relation to your case, and there will be a record about in the GCMS notes usually. That would be another way of knowing.
Just be sure to include, the Application number, Date of Birth and full name, you can also supply the UCI number just to be safe.
best regards
.