Essentially, once you have declared the common-law relationship at the nomination application (i.e. MPNP/Provincial) and your partner has identified you as a spouse/partner under the application filed at MPNP, then you are included in the nomination. If your partner has received your LoA/nomination letter, that should show also who are included in the nomination. With that LoA and onwards to filing the PR application at Federal level (i.e. CIO/CIC), you are included as a spouse (under common-law).
Should you get married, then your status changes from being under common-law to that of being married, which does not have a major impact to the application as the spouse remains the same, and the partnership is still the same, albeit just a change in the nature of the partnership. There is no change in the family members (you) that was included in the application. However, it is still a status change, so down the line, if both of you decide to get married while the application is being processed, then likely you will have to inform the VO, and be required to submit proof of the marriage (Marriage Certificate). Why would this be important? - it all boils down to a change in your identity data - should your name change (i.e. taking the surname of the spouse) then it will have to be reflected in their records as this will have seen in all official documents regarding your residence status (PR cards, CoPR etc.)
/...atb
