Short answer. From the moment you execute the contract. Article 1784 provides that a partnership begins from the execution of the contract, unless it is otherwise stipulated. So it is the agreement itself, not the start of operations or the delivery of contributions, that marks the birth of the partnership — unless the partners fix a different date.
What the law says
A partnership begins from the moment of the execution of the contract, unless it is otherwise stipulated.
Civil Code, Article 1784 — When a Partnership Begins. Read the full provision →
The contract, not the operations
Article 1784 fixes the birth of a partnership at a precise point: a partnership begins from the moment of the execution of the contract, unless it is otherwise stipulated. The partnership comes into being when the partners agree — when the contract is perfected — and not when they open for business, hand over their contributions, or register with any office. A partnership is a consensual contract: it is complete on the meeting of minds. So partners can be bound to one another as a firm before a single peso has been contributed, because it is the agreement, not the activity, that the law treats as the starting line.
'Unless otherwise stipulated'
The rule is a default the partners can move. Because the article applies unless it is otherwise stipulated, the partners are free to agree that their partnership will begin on a later date, on the happening of some condition, or when contributions are actually delivered. What the partners cannot do is have the firm exist for legal purposes before there is a contract at all — the agreement is the earliest possible starting point. So read the agreement: if it names a commencement date, that date controls; if it is silent, the moment of signing does.
Why the start date matters
The commencement date is not a technicality; several things hang on it. From that moment the partners owe one another the duties of partners — good faith, the duty not to compete with the firm, the obligation to contribute what they promised — and the partnership can begin to acquire rights and incur obligations. It also marks the reference point for a partnership's term if one is set, and for working out what belongs to the firm as opposed to a partner's separate dealings. Fixing the date wrongly, or leaving it unclear, can turn into an argument about whether a particular transaction or asset fell inside the partnership or outside it.
Put the date in the agreement
If timing matters to your venture — and it usually does when contributions, deadlines or existing deals are involved — do not leave the start date to inference. Say in the contract when the partnership begins, whether that is on signing, on a fixed future date, or once contributions are made. If you intend to be bound only once everyone has put in their share, write that condition in; otherwise the default makes you partners from signing. And keep the signed, dated agreement, because when a dispute reaches back to 'when did this become a partnership', that document is the answer.