The issue of the seventh day with the new 40-hour workweek has become the hot potato in talks between employers and accountants in Mexico. What seemed like a simple, lifelong calculation is now stuck on a point that neither Congress nor the STPS has wanted to clarify in clear terms: if the worker works five days instead of six, is the famous full day of rest still paid, or can the employer recalculate the daily wage based on the days actually worked? The doubt is not minor: it represents between 14% and 16% of each worker's weekly salary. Here, I break down the topic with the law in hand, the two opposing sides, and a numerical example that any SME owner can take to their office.