Is it permissible for an accountant to request a percentage of the store's profits at year-end in exchange for his diligent work?

There is no objection to requesting a percentage of the profit for the mastery and excellence of work if the employer agrees to it. This falls under the category of increasing and adjusting wages. However, the problem lies in the unknown amount of this percentage, and the general rule for wages is that they must be known. Some of the Tabi'un (followers of the Companions) permitted this, and it is a narration within the Hanbali school of thought. Therefore, it is preferable to request an increase in the fixed salary and avoid the percentage. There is no harm in requesting a salary increase or an incentive for good work. If the employers agree, then so be it. If they do not agree, they are not obligated, and the obligation to increase the salary or leave the job becomes applicable upon contract renewal. This is not among the blameworthy forms of asking, as each party has the right to express its will.