Short answer

During an ongoing one-year lease: No. A landlord cannot unilaterally shorten a fixed term that’s already in force. Any change (e.g., from 12 months to 6 months) requires the tenant’s consent or a contractual clause that clearly authorizes it.
At the end of the one-year term: The landlord may offer a new 6-month lease instead of renewing for a year. The tenant is free to accept, negotiate, or decline; if declined, the lease ends and the landlord may demand turnover—subject to rent-control protections, notice, and proper ejectment procedure.

Governing law & principles

Civil Code on Lease & Contracts
- Mutuality of contracts (Art. 1308): A contract’s validity and compliance cannot be left to the will of one party. A fixed-term lease binds both lessor and lessee for the agreed duration.
- Lease of things (Arts. 1642–1688): These provisions cover duties, remedies, and term rules (including tacit renewals).
Statute of Frauds (Art. 1403[2]): Leases beyond one year must be in writing to be enforceable. (Executed contracts are generally taken out of the Statute, but best practice is a written, signed lease.)
Land Registration rules: Leases exceeding one year may be registered to bind third persons (e.g., a buyer of the property).
Rent Control framework (Republic Act No. 9653, as extended by periodic issuances):
- Applies only to covered units within price thresholds identified by the government.
- Caps annual rent increases; limits eviction to specific grounds (e.g., default, need of owner or immediate family to occupy, authorized repairs, etc.).
- Requires advance written notice for rent increases and certain evictions.
- Changing a lease term does not override these protections if the unit is covered.

Practical takeaway: Start with the written lease. Then check whether the unit is rent-control covered; if yes, overlay those protections.

Mid-term changes vs. end-of-term changes

1) While the one-year lease is still running

General rule: The landlord cannot cut the term to 6 months on their own.
Exceptions (narrow):
- A clear contract clause allowing mid-term modification at the lessor’s option (rare and may be scrutinized; clauses that give one party unilateral power over validity/fulfillment can be void under Art. 1308).
- Mutual agreement: Parties sign a written amendment converting the remaining term to a 6-month arrangement (or ending early and replacing with a new 6-month lease).
- Rescission for breach: If the tenant seriously violates obligations (e.g., non-payment, illicit use), the lessor may terminate for cause under the lease/Civil Code. That is not a “change of term”; it’s a termination for breach and must follow notice and, if needed, court action.

2) At the natural expiration of the one-year term

Landlord options:
- Offer a new 6-month lease (with new rent and terms, within rent-control limits if applicable).
- Decline renewal and require move-out upon expiry (lawful if done properly and not barred by rent-control rules).
Tenant options: Accept, negotiate, or vacate at expiry.
If the tenant stays and the landlord silently consents:
- Tacit renewal (tacita reconducción): An implied new lease arises. Its period follows the rent period (e.g., month-to-month if rent is paid monthly), not another fixed year, and prior restrictions apply. The landlord can later end a month-to-month lease with proper prior notice.

Notices, timing, and documentation

A. Ending or not renewing a fixed term

Provide clear written notice before the last day of the term if you won’t renew or if you’ll renew only on a 6-month basis. While the Civil Code focuses on consent rather than specific notice days for fixed-term expiry, reasonable lead time (30 days is common practice; check your lease) reduces disputes.
Under rent control, separate notice rules may apply (e.g., months-ahead notice for increases or certain evictions). Follow the stricter rule where both apply.

B. Month-to-month situations (implied renewals or no fixed term)

If rent is monthly, the lease is typically from month to month. Ending it usually requires prior written notice before the next period begins (30 days is common practice).
Keep proof of service (personal delivery with acknowledgment, registered mail, or reputable courier).

C. Form & signatures

Use a written, signed document for any amendment or new 6-month lease.
If the total term exceeds one year, keep it in writing and consider notarization and registration to bind third persons.

Interplay with rent control (if applicable)

Changing from 12 months to 6 months is not a loophole to avoid caps or eviction limits.
Rent increases between the expired yearly lease and the offered 6-month lease must respect annual caps and notice under rent control.
Eviction limits still apply; a refusal to accept a proposed 6-month term after expiry is typically resolved by simply ending the lease at term (lawful non-renewal), not by ejectment “for cause,” unless other grounds exist.
If the landlord seeks to recover the unit for owner’s or immediate family’s use, or to perform authorized repairs/renovations, rent-control rules set specific procedures and notice—follow them exactly.

Common scenarios

Landlord wants to “convert” a running 12-month lease to 6 months for a sale
- Not allowed unilaterally. Either negotiate an early termination (possibly with compensation) or wait until expiry. If rent control applies, recovery of premises for sale isn’t generally an ejectment ground; coordinate timing at renewal.
Lease ends; landlord offers only a 6-month renewal; tenant insists on 12 months
- The landlord may stand by the 6-month offer. If the tenant declines, the lease ends at expiry. If the tenant holds over and the landlord accepts rent, an implied month-to-month may arise—landlord can later end it with proper notice.
Tenant holds over quietly after expiry; landlord keeps accepting rent
- Implied lease forms based on rent periods (often month-to-month). Either side may terminate on proper prior notice; rent-control protections, if applicable, still overlay rent increase and eviction rules.
There’s a clause allowing the landlord to “modify terms anytime”
- Such one-sided clauses are suspect and may be void under mutuality principles. Courts look for clear, fair, and mutual modification mechanisms.

Drafting & negotiation tips

Be explicit on term & renewal: State the exact dates, whether it auto-renews, and on what terms (e.g., “converts to month-to-month unless a new fixed term is signed”).
Lock in notice windows: Specify how many days’ notice each party must give for non-renewal or end of a month-to-month tenancy.
Rent-control compliance clause: Affirm that any increases or termination will be subject to applicable rent-control rules.
Early termination clause: If either party needs flexibility, draft a mutual early-termination option with notice period and perhaps reasonable pre-termination fees (lawful and proportionate).
Registration (for >1-year terms): Consider notarization and annotation to protect against third-party claims.

Procedure if negotiations fail

If the fixed term has not expired:
- Landlord must honor the term (unless there’s cause for termination under the contract/Civil Code).
- Attempts to force a mid-term change can expose the landlord to damages or harassment claims.
If the term has expired and tenant refuses to vacate:
- Send final demand to vacate (and to pay, if applicable).
- If the tenant still refuses, file unlawful detainer (Rule on Summary Procedure) in the proper court after mandatory barangay conciliation (Katarungang Pambarangay), when applicable (i.e., parties reside in the same city/municipality and no exceptions apply).

Tenant & landlord duties (quick map)

Landlord: Deliver peaceful possession; maintain the premises for intended use; respect the fixed term; follow rent-control notice/cap rules (if applicable); provide lawful, written notices; pursue legal eviction only through proper process.
Tenant: Pay rent on time; use property as agreed; follow house rules; allow access for necessary repairs on reasonable notice; vacate upon lawful end of lease or agreed termination.

FAQs

Q: My landlord just announced our ongoing 12-month lease is now 6 months. Is that valid? A: No. Mid-term unilateral shortening isn’t valid. Point to the written lease and mutuality rule. You can negotiate an amendment, but you’re not obliged to accept.

Q: The lease is ending next month. Can the landlord insist the renewal is only 6 months? A: Yes. At expiry the landlord can offer new terms (e.g., 6 months). You may accept, negotiate, or decline and vacate on the end date—subject to rent-control rules if applicable.

Q: What if I just stay and keep paying after expiry? A: If the landlord accepts rent without objection, an implied month-to-month lease typically arises. Either party can then end it with proper prior notice.

Q: Does rent control stop a landlord from offering a 6-month term? A: Rent control doesn’t dictate fixed-term lengths, but it limits rent hikes and restricts eviction grounds and notice. The offer of a 6-month renewal must still comply with those rules.

Q: Is oral agreement enough? A: Avoid it. Leases over one year must be in writing to be enforceable; even for shorter terms, a written, signed contract prevents disputes.

Practical checklists

For landlords proposing a 6-month term at renewal

☐ Review lease expiry date and notice clauses
☐ Confirm rent-control coverage and compliance
☐ Serve written offer (term, rent, start/end dates, deposit handling) with reasonable lead time
☐ If declined, prepare turnover plan and, if necessary, lawful ejectment steps

For tenants facing a proposed change

☐ Re-read your existing lease (term, renewal, notice, early-termination clauses)
☐ Check if your unit is rent-control covered
☐ Decide to accept, counter-offer, or vacate; request terms in writing
☐ If landlord insists mid-term, cite mutuality and decline unless you agree to amend

Bottom line

A landlord cannot change a running yearly lease into a 6-month term unilaterally.
At renewal, the landlord may offer only a 6-month term; the tenant may accept or move out at expiry.
Always anchor decisions on the written lease, the Civil Code, and—if applicable—the rent-control rules on increases, notices, and eviction grounds.