https://www.canada.ca/en/immigratio...lass-determining-spouse/assessing-common.html
What is cohabitation?
Cohabitation means living together. Two people who are cohabiting have combined their affairs and set up their household together in one dwelling. To be considered common-law partners,
they must have cohabited for at least one year. This is the standard definition used across the federal government. It means
continuous cohabitation for one year,
not intermittent cohabitation adding up to one year. The continuous nature of the cohabitation is a universal understanding based on case law.
While cohabitation means living together continuously,
from time to time, one or the other partner may have left the home for work or business travel, family obligations, and so on.
The separation must be temporary and short.
Sponsor in Canada and common-law partner abroad
According to case law, the definition of a common-law partner should be read as “an individual who is (ordinarily) cohabiting.” After the one year period of cohabitation has been established, the partners may live apart for periods of time while still maintaining a common-law relationship. For example, a couple may have been separated due to illness or death of a family member, adverse country conditions (e.g. war, political unrest), or employment or education-related reasons, and therefore are not cohabiting at the time an application is submitted.
Despite the break in cohabitation,
a common-law relationship exists if the couple
has cohabited continuously in a conjugal relationship in the past for at least one year and intend to do so again as soon as possible. There should be evidence demonstrating that both parties are continuing the relationship.
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If speed is of the essence, getting married and then applying for spousal sponsorship would be your best (and only) option.
As mentioned, you have not yet qualified to be common-law in the eyes of IRCC, because you have not met the required 365 days (or more) of cohabiting under the same roof. Having a joint lease and a joint bank account, in and of itself, does not change the fact that your girlfriend (who you would refer to as your `partner' if you were common-law) does NOT live with you for ~20 days per month, right? She has the same mailing address, but that's not enough, IMHO.