The short answer
In a sublease, the original tenant stays on the lease and rents part or all of the space to a subtenant, so the landlord's contract is still with the original tenant, who remains liable for rent and every other obligation. In an assignment, the original tenant transfers its entire interest in the lease to a new tenant, who steps into the lease going forward. The practical difference for the landlord is who you can look to if something goes wrong: after a sublease you still hold the original tenant, while after an assignment you may hold only the assignee unless the lease or the assignment document keeps the original tenant on the hook. Most commercial leases require the landlord's consent to either one, and the consent clause is where the landlord's leverage actually lives.
The structural difference, and why it matters
A sublease is a lease within a lease. The original tenant, now acting as a sublandlord, grants a subtenant the right to occupy the space, but the head lease between the landlord and the original tenant stays fully in force. The subtenant has no direct contract with the landlord, pays the original tenant, and the original tenant keeps paying the landlord and performing every lease obligation. If the subtenant stops paying, that is the original tenant's problem, not a change to what the original tenant owes the landlord.
An assignment is a transfer of the whole leasehold. The original tenant hands its entire remaining interest to an assignee, who becomes the tenant under the existing lease for the balance of the term. The landlord's day-to-day relationship shifts to the assignee. What does not automatically shift is the original tenant's liability: depending on the lease language and the law of the jurisdiction, an assigning tenant can remain secondarily liable if the assignee defaults, which is why landlords often insist the original tenant and any guarantor stay bound as a condition of consent.
What changes for the landlord in each case
After a sublease, the landlord's counterparty is unchanged. You still bill the original tenant, still enforce against the original tenant, and generally have no direct claim against the subtenant unless the lease or a separate agreement creates one. The risks that matter are use and occupancy: a subtenant whose business changes the permitted use, triggers a co-tenancy or exclusivity clause elsewhere in the property, or increases wear and insurance exposure. The landlord manages those through the consent conditions and by requiring the sublease to sit subordinate to the head lease.
After an assignment, the landlord's counterparty changes. The credit, operating history, and covenant strength you underwrote at signing may be replaced by an unknown assignee. That is why an assignment usually gets closer scrutiny than a sublease: the landlord is being asked to accept a new principal obligor for the rest of the term. Landlords commonly respond by conditioning consent on financials for the assignee, an assumption agreement in which the assignee expressly takes on all lease obligations, and continued liability from the original tenant and guarantor.
The consent clause is the control point
Most commercial leases prohibit assignment or subletting without the landlord's prior written consent, and the wording of that clause decides how much room the landlord has. A clause that lets the landlord withhold consent in its sole and absolute discretion is very different from one requiring consent not to be unreasonably withheld, which many jurisdictions read against the landlord and which can expose a refusal to challenge. Some leases also give the landlord a recapture right, the option to take the space back rather than approve the transfer, and a right to share in any profit the tenant earns by subletting or assigning above the contract rent.
Because the consent standard, recapture rights, and profit-sharing all live in the specific clause, the landlord's first move on any transfer request is to read the exact language of its own lease rather than rely on habit. What counts as a permitted transfer also varies: many leases carve out transfers to an affiliate or a successor by merger from the consent requirement entirely, so a request that looks like an assignment may not need consent at all under that lease's definitions.
What to pull from the lease before responding
Before granting or refusing consent, the landlord should have the current answer to a short list of questions, each traced to the controlling document: does the lease require consent for this type of transfer, and under what standard; is there a recapture right or a profit-sharing provision; does the original tenant remain liable after the transfer, and does any guaranty continue; are there permitted-transfer carve-outs that make consent unnecessary; and what use, insurance, and subordination conditions should attach to the consent. Because amendments can change any of these, the answers must come from the resolved document chain, not the original lease alone.
This is general information about how sublease and assignment provisions typically operate, not legal advice. How a specific consent standard applies, whether a refusal is reasonable, and what a landlord should require in a consent document are questions that turn on the exact lease language and the governing law, and where real money or a difficult counterparty is involved, they belong with counsel.
Common questions
Is the original tenant released from the lease after an assignment?
Not automatically. An assignment transfers the leasehold to the assignee, but whether the original tenant is released depends on the lease language and the jurisdiction. Landlords frequently condition consent on the original tenant and any guarantor staying liable, so a release usually happens only if the landlord expressly agrees to one.
Can a landlord refuse consent to a sublease or assignment?
It depends on the consent standard in the lease. If the clause lets the landlord withhold consent in its sole discretion, refusal is broad; if it requires consent not to be unreasonably withheld, a refusal generally needs a commercially reasonable basis. The specific clause and the governing law control, so the lease should be read before responding.
Does a subtenant pay rent to the landlord?
Usually no. In a standard sublease the subtenant pays the original tenant, who continues paying the landlord under the head lease. The landlord's contractual relationship stays with the original tenant unless a separate agreement, such as a recognition or attornment agreement, creates a direct link to the subtenant.
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