[Last time we saw that while all agree that an eved ivri who was sick for up to three years does not have to make up time missed, a machloket Rishonim exists regarding a regular worker who is paid for a certain amount of time and missed a significant part of it due to illness. The Tashbetz distinguished between one who works for a long time, in which case, the employer has to expect some illness, to which he apparently relinquishes his claims if he did not stipulate, and a short-term worker.]
Everything we have discussed to this point is according to the halacha as set down in the gemara. However, even the Tashbetz would agree that the matter is affected in our time and place (Israel) by the corresponding legislation on the matter, i.e., The Law of the Payment for Illness. Unless we know otherwise, we can assume that one who hires a worker has in mind to follow the law of the land in this regard and, therefore, he would be required to pay for sick days as the law subscribes, or alternatively as it is customary in a certain place of work. However, in a place where there is apparently no clear practice, it is logical that the parties should follow the law as set down in the Torah sources. The Rosh would presumably agree that when one works in a structured place of work that usually gives sick days, the situation would be one where the employer and employee obligated themselves in this regard as is written in the law or as is customary.
A significant matter of halacha arises in a case where the employer paid in advance. The Rama (Choshen Mishpat 333:5) says that if the employer paid the worker in advance he cannot reduce the salary and thereby demand the worker to return some of the salary. Rav Binyamin Rabinowitz (Hatorah V’hamedinah IX) explains that the difference of whether or not there was advance payment stems from it being a sign of a different type of business agreement. When he pays in advance, it is as if he obtained the body of the worker, making him similar to an eved ivri. Regarding an eved, the employer is the one who is impacted by the inability of his "property" to be productive. Therefore, if he became ill, the employer cannot demand back his salary. In contrast, when the employer pays after the work is done, the worker’s body is not in any manner considered acquired. Then even if he was already been paid in full (after the work), the employer can demand back that which he mistakenly paid corresponding to time that the worker did not work due to illness.