Short answer. No, it does not have to be in writing. Agency may be oral, unless the specific law governing the transaction you're authorizing requires a particular form. Agency can also be implied from a principal's conduct — silence, inaction, or a failure to repudiate someone acting on their behalf — without any express agreement at all.
What the law says
Agency may be oral, unless the law requires a specific form.
Civil Code, Article 1869 — Express or Implied Agency. Read the full provision →
The default rule: no writing needed
The general position is permissive. Article 1869 states plainly that agency may be oral, and the only exception written into that same sentence is where a specific law requires a particular form for that kind of transaction. So the baseline is not "agency needs a document" — it's the reverse: a verbal arrangement is enough, unless some other rule applicable to what the agent is being authorized to do says otherwise.
Express agency is only half the picture
This article recognizes two ways agency can arise. It can be express — spoken or written words actually granting authority. Or it can be implied from the acts of the principal: from the principal's own conduct, from silence or lack of action, or from a failure to repudiate the agency while knowing that someone is acting on their behalf without authority. That means even where nobody ever said "you are my agent," a principal's behavior toward someone acting for them can create the relationship on its own.
Where a specific form becomes mandatory
The oral-is-fine rule yields whenever the underlying transaction the agent will carry out has its own form requirement. If the agent is being authorized to do something the law says must itself be done in a particular way, that requirement carries over to the authority to do it. In that situation, an oral appointment will not be enough for the agent to validly bind the principal in that specific transaction, even though agency in general does not demand writing.
Why you would want it in writing anyway
Legal sufficiency and practical wisdom are different questions. An oral agency can be perfectly valid and still be very hard to prove — its scope, its limits, and even whether it existed at all can become exactly what a dispute turns on once money or property has changed hands. Third parties dealing with your agent, and courts asked to sort out a disagreement later, will look for something concrete to establish what authority was actually given. A written appointment removes that ambiguity even in situations where the law itself would not have required one.
Cases citing this provision
These Supreme Court decisions cite the provision above. We list them so you can read them yourself; the summaries of what each decided are not ours to give.
- Sps. Fernando and Lourdes Viloria vs. Continental Airlines, Inc, G.R. No. 188288, January 16, 2012 — read the decision on LawPhil →
- Yun Kwan Byung vs. Philippine Amusement Gaming Corporation, G.R. No. 163553, December 11, 2009 — read the decision on LawPhil →
- Professional Services, Inc. vs. Natividad & Enrique Agana, G.R. No. 126297, January 31, 2007 — read the decision on LawPhil →
- Samuel Parilla, et al. vs. Dr. Prospero Pilar, G.R. No. 167680, November 30, 2006 — read the decision on LawPhil →