it varies with regarding the category of immigration and the Canadian Immigration visa office where you are applying.

When you are applying under the category of skilled worker/or professional then you have to submit your supporting documents 120 days before the assessing of your application begins.

When you are applying under the category of Family Immigration category then you have to submit all the required documents simultaneously with the initial application.

When you are applying under the Business category then you have to initially submit your application along with the fee at the Canadian Immigration office. Then you will be notified to submit your other supporting documents, at least four months before the assessment of your application form. But when you are applying in the Canadian visa office in Buffalo New York, you should submit all your supporting documents simultaneously with the application.

The supporting documents required must be submitted along the initial application in the province when you are applying under Provincial Nomination Program of Canadian Immigration or if you want to reside in Quebec province.

All supporting documents should be submitted with the initial application when you are applying under the class of Canadian Experience category of Canadian Immigration.