Well, for me what I had is:
1. Photos (In an envelope – written my full name on the back of photos - no UCI since they didn't ask)
2. Application – CIT 002 (signed and dated)
3. Physical presence calculator (signed and dated)
4. Photocopies of valid and expired passports (biographical pages only from both the passports)
5. Copy of confirmation of permanent residence (IMM 5292 or IMM 5688) - asked in the guide but not in the checklist, one of CoPR/PRC/etc
6. Photocopies of proof of English (Diploma certificate)
7. Photocopies of 1 pieces of ID (PR Card only since I had passports in the last 5 years)
8. Receipt of an application fee of $630.00 paid online
I noticed that many are submitting multiple IDs, including driver's license, health card. However, when I checked through the check list and instruction guide, the only think needed is one landing document (CoPR/PRC/etc) and one ID (I used PRC).
I also put my documents in exact order of the Document Checklist in the envelope. I'm sure it's fine. I did the exact same thing with my PR application. I don't think it's essential for the receipt to be on the top and the very first thing they see.
I also only sent in my PR card copy and not my COPR as they did only ask for one landing document. I sent in my driver's licence as my other form of ID.