Regardless of whether there is inheritance or will, and there are several heirs we are dealing with inheritance shares. Each of the heirs has an abstract part of the estate, whose size is indicated by a simple fraction.

When the deceased does not leave a will or for some reason it is invalid, the order and manner of inheritance is determined by the provisions of the Act. We meet the same principle when the persons indicated in the will do not accept the inheritance. Pursuant to the provisions contained in book IV of the Civil Code, the testator's children and his spouse are appointed first. They inherit in equal shares, which means that the inheritance mass is divided into as many parts as the heir had children, with the addition of a spouse to this number. However, the Code stipulates that a spouse may not be entitled to less than a quarter of the estate. As can be seen from the above, this rule only applies if the heir had more than three children. In the event that the child of the testator has not survived the opening of the inheritance, due to his inheritance share falls to his children in equal parts. As in the previous case, the number of shares depends on the number of children.

Subsequently, when the testator had no children, the deceased's parents and spouse are appointed to succeed. Each parent inherits a quarter of the estate, while the remaining spouse ½. When the deceased's father is unknown, the mother inherits all ½. In the absence of both descendants and spouse, the inheritance is inherited by the parents of the deceased, each after ½. If one of the parents of the deceased has not survived the opening of the inheritance, the inheritance that would fall to him shall be given to the siblings of the testator in equal parts. If any of the siblings were dead, inheritance falls to their descendants. In a situation where there are no siblings of the deceased or their descendants, and one of the parents of the testator is dead, the other parent inherits in the coincidence with the spouse ½ of the estate. The inheritance share of the spouse who inherits in the confluence with the parents, siblings and their descendants is always ½. In the absence of the above, the deceased's spouse bears the entire estate. In a situation where there are no descendants, the spouse, parents, siblings and descendants of the testator's siblings, the entire inheritance falls on the testator's grandparents who inherit in equal parts. If any of the grandparents had not survived the opening of the inheritance, the inheritance that would fall to him would fall to his descendants. This share is divided into as many parts as there are descendants. If there are no descendants of the grandparents who did not live to the opening of the inheritance, the inheritance that would fall to him falls to the other grandparents in equal parts. Subsequently, the children of the testator's spouse, so-called stepchildren, may be inherited, but only those whose parents have not survived the opening of the estate. This can only happen if the inheritance of the deceased spouse and relatives of the deceased who were called to inherit under the law did not live to open the estate. Emotional links between the testator and stepchildren are not taken into account. When all the possibilities of transferring the inheritance to natural persons listed in the provisions of the Code are exhausted, the inheritance falls on the commune of the testator's last place of residence. In the event of the impossibility of determining the last place of residence of the deceased or when this place was outside the Republic of Poland, the fall is entirely attributable to the State Treasury.

A will may determine the size of inheritance shares, and when this is not done, the size of the inheritance shares depends on the value of the property that was given to the heir. In the event of a dispute, the amount of the succession shall be determined by the court.