Its not about verification, its about being truthful and following the law. If you did not register your marriage, then how come you are married? And if you are claiming to be unmarried, then there should be no proof present for your marriage.
If you claim that you are unmarried and get a PR successfully, and at a later time it is found that you lied about being married, you can face serious consequences.
More details below:
https://www.canada.ca/en/immigration-refugees-citizenship/corporate/publications-manuals/operational-bulletins-manuals/permanent-residence/non-economic-classes/family-class-determining-spouse/legality.html
Marriage must be valid where it took place and under Canadian law
A marriage that took place abroad must be valid both under the laws of the jurisdiction where it took place and under Canadian federal law in order to be considered legal for immigration purposes. A marriage that is
legally recognized according to the law of the place where it occurred is usually recognized in Canada, but the onus is on applicants to prove that their marriage is legal.
Marriages performed in embassies or consulates must meet the requirements of the host country in which the mission is located. A diplomatic mission or a consular office is considered to be within the territory and jurisdiction of the host (receiving) state. Therefore, a marriage performed in an embassy or consulate must be legally recognized by the host state in order to be valid for Canadian immigration purposes. An applicant who married in an embassy or consulate must satisfy an officer that all of the requirements of the host country with respect to marriage have been met, including whether the host country recognizes marriages performed in diplomatic missions or consular offices within its jurisdiction. Exceptions to this requirement are rare.
The most common impediment to a legal marriage is a
previous marriage that has not been dissolved. Marriages are dissolved through annulment, divorce or the death of one of the parties.
What to do if a marriage is not legal where it occurred
Some marriages may not be legal where they occurred (e.g. defect in capacity [who can marry whom], marriage in an embassy is not recognized by the host country, religious prohibitions, form of ceremony not permitted), but the marriage would otherwise be recognized in Canada. Officers should explain to the applicant that they do not qualify as a spouse because their marriage is not legal where they married, but that they might qualify if they marry in another jurisdiction where their marriage would be legal.
If re-marriage in another jurisdiction is not feasible, and if the relationship between the sponsor and applicant is genuine and the relationship meets the requirements of either
common-law partner or
conjugal partner, they may be processed as such. Consult the applicant before processing their application in another category.
If applicants qualify as common-law or conjugal partners, explain that their marriage will not be recognized as legal in Canada. If they wish to be recognized as a married couple, they will have to marry in Canada. If they are conjugal partners, explain that they must live together in a conjugal relationship for one year before either can exercise any rights or privileges associated with common-law status.
The applicant must meet the definition of common-law partner or conjugal partner at the time the sponsorship and permanent residence applications are submitted, i.e. for common-law partners, they must have lived together continuously in a conjugal relationship for at least one year, and for conjugal partners, they must have been in a conjugal relationship for at least one year.
If the applicant is unwilling to be considered as a common-law or conjugal partner, or is unable to provide satisfactory evidence of a conjugal relationship, the application should be refused.
