G.R. No. 104404 - Spouses Tiu Peck and Lee Yok Yan vs. Court of Appeals

Joaquin Tiu Singco, father of petitioner Tiu Peck, owned and managed Argentina Trading, a lumber, hardware, and general merchandise business in San Marcelino, Zambales.
Tan King and Conchita M. Rubiato assisted in business management and marketing, receiving monthly salaries, although the business license was in Rubiato's name.
After Joaquin's death in 1974, Tiu Peck took over the business with Tan King and Rubiato continuing their involvement, eventually becoming partners.

In 1983, petitioners (Tiu Peck and Lee Yok Yan) and private respondents (Tan King and Conchita Rubiato) decided to terminate their business partnership.
They enlisted five respected members of the Filipino Chinese Chamber of Commerce and Industry as mediators.
On August 31, 1983, they entered into an "Agreement on the Apportionment of Partnership Businesses," which outlined:

Division of the joint business by lottery.
Phased collection and commission scheme for accounts receivable.
Appropriation of funds for employee separation and unpaid taxes.
Estimated asset values of the lumber/hardware business (₱1.6 million) and piggery (₱1 million).
Payment terms between the winners of the respective lots.

The lottery resulted in Tiu Peck acquiring the lumber and hardware business, and Tan King acquiring the piggery business.
Both parties took possession and operated their respective businesses accordingly.

After three years (on April 21, 1986), the private respondents demanded partition and subsequently filed an action to partition the land parcels where the respective businesses were located.
The Regional Trial Court (RTC) ruled that the lots and buildings involved are owned in common pro indiviso by both parties, ordering their partition.
Petitioners appealed to the Court of Appeals (CA), which partially modified the RTC ruling but still declared joint ownership with an order for partition under Rule 69 of the Revised Rules of Court.
Petitioners thereafter filed a petition for review on certiorari before the Supreme Court, challenging the CA's ruling on several grounds including disregard for the executed partition agreement, breach of contract principles, equity considerations, and estoppel.

Whether a valid business partnership existed between petitioners and private respondents given the absence of a formal public instrument and SEC registration.
Whether the "Agreement on the Apportionment of Partnership Businesses" dated August 31, 1983, is valid and binding, precluding a new partition suit.
Whether the Court of Appeals erred in declaring the properties as owned in common pro indiviso and ordering a new partition despite the executed agreement and subsequent implementation of its terms.
Whether principles of contract law, equity, and estoppel bar the private respondents from challenging the partition agreement after three years of compliance and possession.