Generally, the first step in attempting to break a fixed-term lease (where nobody has violated the lease) would be to discuss the situation with the other party. If both parties consent to end the lease early, it can be terminated with a Termination Agreement.
If terminating a lease is not an option, subleasing or assigning may be a good alternative for both parties.
To sublease a rental property, a landlord provides their consent to sublease so the tenant can create a Sublease Agreement with a subtenant. The original tenant remains liable for the obligations stated in the original lease agreement.
Assigning a lease means transferring lease interest to a new tenant. Unlike subleasing, assigning means the original tenant gives away their rights and obligations to the new tenant. To assign a lease, a landlord provides their consent to assignment, and the parties use a Lease Assignment Agreement to outline the arrangement.
If one party has substantially breached the lease terms, the other may be entitled to end the lease early. If a landlord has legal cause to terminate a lease early, they inform the tenant to vacate the rental property with an Eviction Notice. Alternatively, a tenant uses a Termination Notice.
Landlords can also end a lease based on a lesser breach if they give the tenant a sufficient chance to remedy the problem and they don't do so.