To be on the "safe" side of things, I would recommend that you make sure, 100% you have these:
IELTS test score sheet, (remember it can't be older than 2 years by time of submission)
Police clearances certifications, (no older than 3 months from time of issue to time of submitting application), for all places where you have lived longer than 6 months.
ECA for all the studies you are going to claim points for.
Work references where you can see period of employment, full time/part time, description of duties (preferably per NOC list), personal references, academic references.
Identification CURRENT documents such as passports, ID's, marriage certificates, birth certificates... I am using plural to explain that all these for all applicants intended.
All these docs are mandatory, my recommendation (and I know there is going to be people here screaming on this list), is that if you can have all this ready before hand, you are going to be ahead of many, many applicants... take a look of other topics and you'll see.