The bargaining relationship is between the union and the employer. There are many reasons why this relationship may change over time, for example if a unionized business is sold, leased or transferred, a union merges or reorganizes, the bargaining agent changes, or a common or true employer is declared.
If a unionized business, or a part of it, is sold, leased, transferred, or otherwise disposed of, the union's bargaining rights and any collective agreement are transferred to the new business. This transfer of the union's bargaining rights is called a successorship.
Sometimes unions merge or reorganize themselves. The bargaining rights the unions held before the change can transfer to the merged or reorganized union (called the successor union). The transfer of bargaining rights from the original union (called the predecessor union) to the successor union is known as a union successorship.
There are a number of reasons why the trade union representing a group of employees can change. Sometimes the union initiates the change. Other times, a different union organizes the employees and initiates the change by applying for certification.
The Board can declare that two or more provincial entities (i.e. companies or institutions) are one employer for the purposes of the Labour Relations Code. This is called a common employer declaration. The Board can also declare that another company or institution is the true employer of the employees. This is called a true employer declaration.