Short answer. Generally no. Article 100 is the non-diminution rule: nothing in this Book is to be construed to eliminate or in any way diminish supplements or other employee benefits being enjoyed. A benefit that has become an established part of the terms of employment cannot simply be withdrawn at the employer's convenience.
What the law says
Nothing in this Book shall be construed to eliminate or in any way diminish supplements, or other employee benefits being enjoyed
Labor Code, Article 100 — No Diminution Of Benefits. Read the full provision →
Reduction counts, not only removal
The words are eliminate or in any way diminish. So the rule is not confined to an allowance being stopped outright: cutting the amount, narrowing who receives it, adding conditions that were never there, or converting a monthly payment into an occasional one are all diminutions of a benefit being enjoyed. Employers frequently restructure rather than abolish, and the restructured version is what has to be compared with what went before. The comparison is of substance and value, not of the name the payment carries.
What makes a benefit protected
Not every payment ever made becomes untouchable. What the rule protects is a benefit genuinely being enjoyed — one granted consistently and deliberately over a considerable time, so that it has become part of what employees are engaged on rather than an occasional act of generosity. Two things therefore matter: how long and how regularly it was given, and whether the employer meant to give it. A payment made by mistake, or once in a good year, is on a different footing from an allowance paid every month for years.
Where withdrawal can be legitimate
There are situations in which a benefit properly ends: it was expressly given for a fixed period or a stated purpose that has passed, it was conditional on something that is no longer true, or it is being replaced by an arrangement the employees have actually agreed to. Genuine agreement is the important qualifier. A memo announcing the change, or a signature collected in the same breath as a payslip, is not the same as a negotiated variation of terms, and it does not become one because nobody objected at the time.
Document the practice before it disappears
The claim rests on showing the pattern. Collect payslips over as long a span as you can, any memo or policy that announced the benefit, and the notice or memo withdrawing it. Note how many people received it and for how long, because a benefit given across a group is easier to establish than one given to you alone. If the employer has offered a reason for the withdrawal, get that in writing too — it often defines the ground on which the dispute will be argued.