If you have received payments from an organization, you may be receiving a T4A slip from them.
The CRA currently dictates that a T4A must be issued to any entity that provides a service (i.e. not goods) and is paid over $500 in a year.
It does not matter if the entity providing the service is an individual or a corporation. It does not matter if the entity invoiced for the services or not. It does not matter if the entity charged or did not charge GST on the invoice. Any service over $500 requires a T4A slip.
CRA refers to guide RC4157.