Short answer. It depends entirely on why you used it. Article 178 of the Revised Penal Code punishes the public use of a fictitious name only where the purpose is to conceal a crime, evade the execution of a judgment, or cause damage. Without one of those purposes, no offence is committed.
What the law says
any person who shall publicly use a fictitious name for the purpose of concealing a crime, evading the execution of a judgment or causing damage
Revised Penal Code, Article 178 — Using A Fictitious Name. Read the full provision →
What the law says
Any person who conceals his true name and other personal circumstances shall be punished by arresto menor or a fine not to exceed Forty thousand pesos (₱40,000).
Revised Penal Code, Article 178 — Using A Fictitious Name. Read the full provision →
The purpose is the offence
The article reaches any person who shall publicly use a fictitious name for the purpose of concealing a crime, evading the execution of a judgment or causing damage. That closed list of three purposes is doing all the work. A pen name on a novel, a stage name, a screen name in a game, a shortened name a person has answered to for thirty years — none of these is a crime, because none of them is aimed at hiding an offence, dodging a court's writ, or hurting anybody. Conversely, a completely ordinary-sounding name becomes criminal the moment it is worn to stay ahead of a warrant or to slip past a creditor enforcing a judgment against you.
What 'publicly' and 'damage' mean here
Two limits are easy to miss. First, the use must be public. A false name whispered to one person in private does not fit the first paragraph, though it may create other problems. Second, causing damage is not confined to money. Damage to reputation, to a person's standing, or to someone's ability to enforce a right can be enough. Note also what the article does not require: nobody needs to have actually been deceived, and no loss needs to have crystallised. It is the purpose behind the public use that the law punishes, so the offence can be complete before the intended harm ever lands.
The lighter second offence, and the penalties today
The second paragraph is a different and lesser wrong: Any person who conceals his true name and other personal circumstances shall be punished by arresto menor or a fine not to exceed Forty thousand pesos (₱40,000). This is concealment rather than the adoption of an invented identity, and it needs none of the three purposes. The first paragraph carries arresto mayor and a fine not exceeding one hundred thousand pesos. Both peso figures come from Republic Act No. 10951 (2017), which revised the fines throughout the Revised Penal Code. Older printings still carry the 1930 amounts, which are far smaller, so check which version of the Code your source is reproducing before you rely on a number.
Where a false name pulls in heavier laws
A borrowed name rarely stays a single problem. Writing another person's name on a document turns the matter into falsification under Articles 171 and 172, which are far graver than Article 178. Using a false identity to obtain money or property is estafa. And when the identity is assumed online — a duplicate profile, an account opened in someone else's name — the cybercrime law of 2012 comes in, since computer-related identity theft is a distinct offence under that statute with its own penalty. If your own name is being used by somebody else, preserve screenshots, links and dates before the account vanishes. If you simply want to be known by a different name lawfully, there is a formal route through the civil registry or the courts, and taking it removes the question altogether.
Related provisions
- Revised Penal Code, Article 178 — Using A Fictitious Name
- Revised Penal Code, Article 171 — Falsification By Public Officer
- Revised Penal Code, Article 172 — Falsification By A Private Individual