Short answer. Yes. Article 97 entitles a prisoner whose conduct is good to deductions from the period of his sentence, rising the longer he has been imprisoned. The figures in the original text have since been revised upward by later legislation, so the allowance actually credited is computed under the amending law.
What the law says
shall entitle him to the following deductions from the period of his sentence
Revised Penal Code, Article 97 — Allowance For Good Conduct. Read the full provision →
It is an entitlement, not a favour
Article 97 provides that the good conduct of any prisoner in any penal institution shall entitle him to the following deductions from the period of his sentence. The word to notice is entitle. The allowance is not a discretionary act of mercy granted case by case; it is a credit the Code attaches to conduct, applied against time to be served. That is why it matters practically to families trying to work out a release date: the sentence pronounced in the judgment is a starting figure, and the time actually served may be shorter.
The credit grows with the years served
The article sets out a graduated scheme rather than a flat rate. The monthly deduction is smallest in the earliest years of imprisonment and increases in steps as the years accumulate, so a long sentence attracts a proportionately larger total allowance than a short one. The specific day figures printed in the original article are no longer the operative numbers — later legislation revised the allowances upward and altered the tiers. Anyone computing a release date must work from the amending statute and its implementing rules, never from an old printing of the Code.
Good conduct is a condition, and it can be lost
The deduction is earned month by month for behaviour in the institution, which means it is not credited in advance and is not immune from being withheld. Misconduct, disciplinary findings and escape all bear on it. The Code places the allowance among the ways a penalty is partially extinguished rather than among the ways criminal liability disappears altogether, which is the right way to think about it: the conviction stands, the record stands, and what changes is the length of time to be served under it.
Where the actual computation comes from
The document that answers a family's real question is not the Code but the institution's own computation of time served, which records the sentence, the credits allowed and the projected release date. Ask for it, and check it against the judgment. Where preventive imprisonment was served before conviction, that is a separate credit with its own rules and it should appear in the same computation. If the figures do not reconcile, or a credit appears to have been withheld, that is a matter to raise with counsel rather than to argue at the gate.