Here's a notice from the CIC - keep track of the acronyms if you can...
On December 19, 2012, the Government of Canada published regulations that will change the way Human Resources and Skills Development Canada (HRSDC) processes offers of arranged employment for the Federal Skilled Worker Program (FSWP).
Currently, employers seek an Arranged Employment Opinion (AEO) from HRSDC when they wish to hire a foreign national on a permanent, full-time basis and support their employee’s application for permanent residence through the FSWP.
Starting on May 4, 2013, most offers of arranged employment will require a Labour Market Opinion (LMO) from HRSDC in support of an FSWP application, instead of an AEO.
LMOs are currently used in the Temporary Foreign Worker Program, as employers often must apply for authorization from HRSDC before hiring temporary foreign workers.
LMOs assess whether there are Canadians or permanent residents available to do the job. This will not change.
Employers will be able to use a single application for an LMO, whether it is being used to support the issuance of a temporary work permit or a permanent resident visa.
AEO letters provided by HRSDC to employers under existing regulations will no longer be accepted by CIC if the FSWP application is received on or after May 4, 2013.
Read the rest here