Short answer. A fine and imprisonment. The Labor Code punishes anyone who commits fraud, collusion, falsification, misrepresentation of facts or any other anomaly to secure a benefit under this Title, with a fine and imprisonment in the amounts and terms the article sets, at the discretion of the court.
What the law says
Any person who, for the purpose of securing entitlement to any benefit or payment under this Title, or the issuance of any certificate or document for any purpose connected with this Title, whether for him or for some other person, commits fraud, collusion, falsification, misrepresentation of facts or any other kind of anomaly
Labor Code, Article 207 — Penal Provisions. Read the full provision →
The provision reaches further than the claimant
Two phrases widen it considerably. It applies to any person, not only to the worker claiming, and it covers acts done whether for him or for some other person — so someone who falsifies a document to help a relative or a colleague is squarely within it. It also reaches beyond the benefit itself to the issuance of any certificate or document connected with the Title, which is where medical certificates and employer records come in.
Some offenders face heavier consequences
The article graduates the penalty by who committed the act. Where the offender has been or is employed by the Commission or System, or is a recidivist, the imprisonment is not less than one year. A lawyer, physician or other professional is, in addition to the penalty, disqualified from practising his profession. An official, employee or personnel of the Commission, the System or any government agency is dismissed, with prejudice to re-employment in government service. The insiders are treated most severely, which is the point of the graduation.
Recovery is separate from punishment
The criminal penalty does not stand alone. Under the logbook provision of the same Title, where benefits are paid on a claim later determined to be fraudulent and the employer is found to be a party to the fraud, the employer must reimburse the System the full amount of the compensation paid. So a fraudulent claim can produce both a prosecution of the individuals involved and a civil restitution obligation, and being cleared of one does not dispose of the other.
Where honest claimants get into trouble
Most people asking this are not planning a fraud — they are worried about an inconsistency. The article targets deliberate falsity, so an error corrected promptly is a different thing from a fabricated account. If a form was filled in wrongly, a date misremembered, or a medical history stated inaccurately, correct it in writing as soon as you notice rather than letting the file carry it. And do not let anyone else complete or embellish your claim documents on your behalf.