In order to hire a foreign worker, Canadian employers may need to satisfy Employment and Social Development Canada (ESDC) that they cannot find any Canadian citizens or Permanent Residents to fill the available position. ESDC's role is to ensure that Canadian residents have first access to Canadian jobs. To better reflect Canada's evolving labour needs, ESDC has recently altered employer requirements for hiring from abroad.

To obtain permission to hire a foreign worker, Canadian employers must first apply to ESDC for a Labour Market Opinion (LMO), however there are exceptions to this rule (referred to as LMO exemptions). The LMO is an assessment of the current Canadian labour market, which ensures that there are no Canadian citizens or Permanent Residents available to fill the positions being offered.

An important element of the assessment is the minimum advertisement requirement for the position. Previously, certain occupations were subject to different advertising time requirement.

As of January 1, 2009, Canadian employers who wish to hire workers from abroad for any occupation must satisfy ESDC that they have advertised the position to Canadian residents for at least 14 days, homogenizing the time requirement. However, the specific details of Canadian employer advertising requirement remain dependent upon where the occupation fits in Canada's National Occupational Classification (NOC) system.

As a general rule, the more complex the position for which a foreign worker is being hired, the less stringent are the advertising requirements.

• Canadian employers who wish to hire foreign workers for management positions or for occupations that generally require a university degree (occupations listed in NOC 0 or A) must advertise the position on Canada's national job bank for at least 14 days or conduct similar recruitment activities in line with occupational standards.
• If hiring for occupations which usually require a college education or apprenticeship training (NOC B), Canadian employers must advertise the position on the national job bank for at least 14 days. This cannot be substituted for other recruitment activities. Additionally, the employer must disclose the wages being offered along with the employer name and address in the advertisement.
• To hire foreign workers for occupations that require high-school education or specific occupation training (NOC C or D), Canadian employers must advertise the position on the national job bank for at least 14 days and must conduct similar recruitment activities in line with occupational standards. They are also required to demonstrate ongoing recruitment efforts in Canadian communities which often face barriers to employment (disadvantaged groups, older workers, etc.).

For all categories, the required advertising must have been carried out no more than three months prior to the application for an LMO.