Short answer. No, not under this article. The law requires overtime work to be paid an additional compensation equal to the regular wage plus at least 25%, on top of what is otherwise owed — meaning actual work beyond eight hours a day is meant to be compensated separately, not absorbed into a fixed salary that assumes it away.
What the law says
Work may be performed beyond eight (8) hours a day provided that the employee is paid for the overtime work, an additional compensation equivalent to his regular wage plus at least twenty-five percent (25%) thereof.
Labor Code, Article 87 — Overtime Work. Read the full provision →
The word doing the work in this article is "additional"
Article 87 conditions overtime work on the employee being paid "an additional compensation equivalent to his regular wage plus at least twenty-five percent (25%) thereof." The article frames overtime pay as something added on top of the regular wage, not as something a regular wage — however it is structured — already accounts for. Work performed beyond eight hours a day is what triggers this additional payment, regardless of whether the employee's pay is computed daily, or expressed as a fixed monthly figure.
The rate itself, and what it is calculated on
The additional compensation is pegged to the employee's regular wage, plus a minimum of twenty-five percent of that regular wage, for every hour worked beyond eight in a day. This is the article's floor — it sets the minimum extra amount owed for overtime hours actually worked, calculated against the employee's own regular wage as the baseline, rather than against some separate or lower reference rate.
The higher rate for holidays and rest days
The article adds a separate, higher rate for overtime performed on a holiday or rest day: work beyond eight hours in that situation "shall be paid an additional compensation equivalent to the rate of the first eight hours on a holiday or rest day plus at least thirty percent (30%) thereof." So the twenty-five percent floor is not universal — overtime on a holiday or rest day is calculated against the holiday or rest-day rate itself, with a thirty percent addition rather than twenty-five.
What this means for a fixed monthly arrangement
Because the article ties overtime pay to actual hours worked beyond eight in a day, being paid a fixed monthly amount does not, by itself, answer whether overtime has already been accounted for — that depends on how the specific pay arrangement was structured and whether it was designed to satisfy this additional-compensation requirement. What the article does establish is that overtime work performed is meant to be compensated on top of the regular wage, not treated as free simply because pay is not computed hour by hour.