[Letter Seeking Legal Advice]
Note: This portion does not identify actual names of persons or companies.

Dear Attorney,

I hope this letter finds you well. I am writing to seek your guidance on a matter related to a land purchase agreement. Recently, I entered into a preliminary written agreement with a seller for the purchase of a lot. The agreement clearly indicated a specific purchase price, and I subsequently made an initial payment towards that amount. However, I have reason to believe that the seller might now be considering an increase in the agreed-upon price, despite the initial payment having already been made under the terms we set forth at the start.

I am concerned that such a unilateral change in price would be unfair or contrary to the conditions of our agreement. Before I proceed with further steps, I would greatly appreciate your professional insight into the legal principles that apply to this situation under Philippine law. Particularly, I would like to know whether the seller can legally adjust the lot price upward after I have made the initial payment and whether I have legal recourse to enforce the originally agreed-upon amount.

Thank you very much for your time and attention.

Sincerely,
A Concerned Property Buyer

[Legal Article]

This comprehensive legal article is written by a highly competent Philippine lawyer and is intended to provide a thorough and meticulous analysis of the issue.

I. Introduction
The question of whether a seller of real property (specifically, a lot) can alter the agreed purchase price after the buyer has already made an initial payment is one that involves contract law, obligations and contracts principles under the Civil Code of the Philippines, and potentially other statutes and jurisprudence that may come into play. In principle, contracts in the Philippines are agreements that the parties must observe in good faith once perfected. The perfection of a sale occurs when the parties have agreed upon the object and price. Once these essential elements are met and an agreement (whether preliminary or final) is reduced to writing and acknowledged by both parties, it generally becomes binding and enforceable. Any attempt to unilaterally modify such essential terms—like the purchase price—without the other party’s consent may give rise to a host of legal and equitable remedies in favor of the non-consenting party.

II. Legal Basis in Philippine Law: The Civil Code and Obligations and Contracts

Fundamental Principles:
Under the Civil Code of the Philippines, a contract of sale is perfected at the moment there is a meeting of minds upon the thing which is the object of the contract and upon the price. Articles 1305 to 1317 of the Civil Code establish the general rules on consent, object, and cause of contracts. Article 1318 provides that there is no contract unless the following requisites concur: (1) consent of the contracting parties; (2) object certain which is the subject matter of the contract; and (3) cause of the obligation which is established. In a contract of sale, the cause is the obligation to deliver the thing sold and the obligation to pay the price.

When the parties have agreed on the lot (its description, boundaries, title status) and a purchase price, and both have consented to these terms, the contract to sell or contract of sale is deemed perfected. Once perfected, neither party can, as a general rule, unilaterally vary the terms of the contract.
Essential Elements and Enforceability:
The price must be certain and definite. Article 1469 of the Civil Code states that the price of a contract of sale must be certain, or at least capable of being ascertained. This definiteness is crucial. If the buyer and seller have agreed on a fixed price and the buyer partially performs by making an initial payment, the buyer’s performance supports the conclusion that a binding agreement exists. At this point, any attempt by the seller to increase the price unilaterally would be a modification that the buyer has not agreed to. This would run counter to the principle that “no one may be permitted to change his mind at will when another party has begun performing his obligations based on good faith and reliance on their agreement.”
Form Requirements:
While the Statute of Frauds (Article 1403 of the Civil Code) requires certain contracts—such as those involving the sale of real property—to be in writing to be enforceable, the presence of a written agreement signed by both parties over the land purchase solidifies the enforceability of the contract. Once reduced in writing and signed, the terms become all the more compelling. Courts in the Philippines generally uphold written contracts as the best evidence of the terms agreed upon by the parties.
Obligation to Act in Good Faith:
Philippine law imposes upon parties the duty to treat each other fairly and to observe good faith and fair dealing. Under the Civil Code, obligations must be performed in good faith, and parties must observe honesty and fairness. If a seller tries to increase the price after having received partial payment, a court could consider such an action as done in bad faith, especially if the buyer has already commenced performance by making an initial payment based on the originally agreed-upon price.

III. Legal Remedies for the Buyer
If a seller attempts to unilaterally alter the contract price after an initial payment has been made, the buyer has several potential remedies:

Specific Performance:
The buyer may file an action for specific performance to compel the seller to adhere to the original contract. If the buyer can prove the existence of a perfected sale or a binding promise to sell at a certain price, and that the partial payment was received, the court may order the seller to complete the transfer of the property at the agreed-upon price.
Rescission and Damages:
Should the seller refuse to honor the original contract price, the buyer may opt to seek rescission of the contract. Under Article 1191 of the Civil Code, the power to rescind is implied in reciprocal obligations when one of the parties fails to comply with what is incumbent upon him. Here, the buyer may argue that by refusing to proceed at the agreed price, the seller has failed to comply with the essential terms of the contract. In such a scenario, the buyer may seek to recover the initial payment plus interest and damages for any loss incurred. This remedy places the parties back to their original positions before the contract, but it allows the buyer compensation for the breach.
Damages for Breach of Contract:
If the seller insists on a price increase, the buyer may also claim damages sustained because of the seller’s refusal to honor the original terms. This can include expenses incurred in reliance on the agreed price, such as costs of preliminary surveys, document preparation, legal consultations, or other foreseeable losses.
Legal and Equitable Defenses:
The buyer may invoke principles of equity. The doctrines of estoppel and laches can also come into play. If the buyer relied on the originally agreed price and acted in good faith (e.g., by making partial payment, securing financing arrangements, or making improvements in anticipation of the transaction’s completion), courts may refuse to allow the seller to benefit from a sudden change of terms.

IV. Jurisprudence and Illustrative Cases
While Philippine jurisprudence generally favors holding parties to their original agreements, some Supreme Court decisions have made it clear that once a contract is perfected, any substantial alteration of an essential term—like price—requires mutual consent. A unilateral increase is generally disfavored.

For example, the Supreme Court has repeatedly ruled that the terms of a perfected contract cannot be altered without the consent of both parties. If the seller attempts to raise the price after partial payment, courts are likely to find that such a move is invalid. Although not every single scenario is identical, the underlying principle remains consistent: the mutual assent of the contracting parties is required to modify the terms of a perfected contract.

V. Special Situations and Exceptions

Condition Precedents or Contingencies:
In rare cases, an initial agreement might contain terms that make the final purchase price contingent upon certain events, such as the completion of a re-survey, resolution of encumbrances, or verification of the property’s exact size. If the initial agreement was incomplete, stating merely a provisional price subject to final verification of land area or improvements, then the price could be adjusted according to a previously agreed formula or condition. However, absent such a valid contingency clause, the price cannot be changed arbitrarily.
Sale by Installments and the Maceda Law (R.A. 6552):
In cases involving installment sales of real property, the Maceda Law grants certain rights and protections to buyers who have paid a certain percentage of the purchase price. While this law primarily deals with the rights of buyers to refunds, grace periods, and the forfeiture of partial payments, it also stands as a testament to the legislative intent to protect buyers from unjust or arbitrary changes in conditions. Although the Maceda Law focuses more on forfeiture and refunds rather than unilateral price increases, its protective stance on buyers under installment contracts underscores the principle that sellers must adhere to the original terms once performance has begun.
Subdivision and Condominium Buyers Under P.D. No. 957:
For sales of subdivision lots or condominium units regulated by Presidential Decree No. 957 and its implementing rules, the Housing and Land Use Regulatory Board (HLURB, now reconstituted as the Department of Human Settlements and Urban Development or DHSUD) provides additional layers of protection. Sellers and developers are bound to the prices and terms they disclose in their license to sell and advertisement materials. Unilateral increases not agreed upon in the original contract might invite administrative sanctions. Although this scenario involves a broader regulatory framework, the principle is similar: sellers are not generally free to unilaterally alter previously agreed-upon prices.
Good Faith Negotiations for Amendments:
Parties may mutually agree to amend contracts. If the buyer and the seller both decide to revise the terms—possibly because of unforeseen circumstances, like significant changes in market conditions or the discovery of a title defect that requires costly remediation—they could negotiate a new price. However, any such amendment requires the informed consent and consideration of both parties. Absent mutual agreement, the seller cannot force a price increase on the buyer.

VI. Practical Steps for Buyers Facing a Price Increase Demand

Review the Written Agreement:
The buyer should carefully review the original contract or agreement. Look for clauses that might allow the seller to adjust the price, whether based on lot size verification, taxes, fees, or any contingencies. If no such clauses exist, the buyer is likely in a strong legal position.
Gather Evidence of the Agreement and Payment:
The buyer should keep copies of all documents—contracts, deeds of conditional sale, receipts of partial payment, correspondence with the seller, and any other communications confirming the agreed price. Such documents will be crucial in a legal dispute.
Send a Formal Demand Letter:
If the seller insists on increasing the price, the buyer can send a formal demand letter reminding the seller of their obligations under the original agreement and requesting compliance with the original terms. This may prompt the seller to reconsider.
Seek Legal Counsel:
Consulting with a qualified attorney is advisable. A lawyer can assess the specific facts and advise the buyer on the best course of action. A lawyer might also represent the buyer in negotiations or, if necessary, in litigation.
Consider Mediation or Alternative Dispute Resolution (ADR):
Before resorting to litigation, the buyer and seller could attempt mediation or arbitration. Sometimes, misunderstandings or disagreements can be resolved amicably. Still, any revised agreement must be voluntary and not coerced.

VII. Conclusion
Under Philippine law, once a contract for the sale of a lot is perfected and both parties have agreed upon the price, that price becomes a key term of the contract. If the buyer has already made an initial payment in reliance on the agreed-upon price, the seller has even less latitude to alter that price afterward. Unilateral price increases not mutually agreed upon are generally considered a breach of contract. The buyer would typically have strong grounds to insist on specific performance at the original price or, if necessary, seek legal remedies, including rescission and damages.

The Philippine legal system seeks to maintain fairness, protect contractual relationships, and enforce the principle that parties must abide by their agreements once perfected. While there may be exceptional scenarios where a price adjustment is warranted due to contingencies or mutual agreement, absent those exceptions, the seller does not have the unilateral right to raise the price after receiving partial payment. Good faith, fair dealing, and the sanctity of contracts remain paramount considerations in resolving disputes of this nature.