Short answer. Yes. The allowance is graduated. The deduction earned for each month of good behaviour is smallest in the earliest years of a sentence and rises in steps as the years pass, with the highest rate reserved for prisoners in their eleventh year and beyond.
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 →
The allowance is built in bands, not as a single rate
Art. 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, and then sets out four bands. The first covers the opening two years of imprisonment. The second runs from the third year to the fifth, the third from the sixth year to the tenth, and the last covers the eleventh year and every year after it. Each band carries a larger deduction for every month of good behaviour than the band before it, so a prisoner deep into a long sentence earns credit faster than one who has just arrived.
The credit is earned month by month, not granted in advance
The deduction attaches to each month of good behavior, which means it accrues as conduct is recorded rather than being fixed at the start of the sentence. A month in which conduct is not good does not produce credit, and the total a prisoner ends up with is the sum of what was actually earned across the bands he passed through. This is also why the arithmetic cannot be done from the length of the sentence alone. It has to be done from the institution's own record of the prisoner's behaviour over time.
The numbers printed in the Code are not the current ones
This is the part that catches families out. The article as originally enacted is reproduced on this site word for word, but later legislation revised the good conduct allowance, increasing the deductions and changing other aspects of how the allowance works, including who may earn it. The graduated structure described above survived that revision; the figures did not. So nobody should compute an expected release date from an old copy of the Code, and any computation that matters should be checked against the current text of the law and against the records actually kept for the prisoner.
What a family should be asking for
The document that governs is the judgment as finally imposed, read together with the prison record of conduct and of any credit already applied. Time spent in detention before conviction is dealt with by its own rules and is a separate question from good conduct credit, though both bear on the same release date. If a computation you have been given does not match what you expected, ask for the written basis of it rather than a verbal figure, and take that paperwork to a lawyer who can check it against the current law.
Related provisions
- Revised Penal Code, Article 97 — Allowance For Good Conduct
- Revised Penal Code, Article 96 — Effect Of Commutation