Would you explain why it is important to receive a dispensation if you must miss Sunday Mass?
Let us consider first what a dispensation is and how it is given. Canon Law includes laws governing the necessity of Sunday and Holy Day Masses. Canons 1246-1247 speak of Sundays and the Holy Days, articulating the obligation of the faithful to participate in Masses on these days (and to abstain from work or business that would inhibit one from giving God His due worship). Other canons speak of the granting of dispensations. Canons 85-93 speak in general of the granting of dispensations from law by bishops and parish priests, and the conditions for granting any dispensations.
The conditions for granting any dispensations are threefold: first, there must be a just and reasonable cause for a dispensation, “taking into account the circumstances of the case and the importance of the law from which the dispensation is given” (cf. canon 90). This means that the law which is being dispensed (in this case, the Sunday obligation) must be weighed along with the circumstances. Not all laws carry the same weight. To dispense from the obligation of Sunday Mass is of greater consequence than dispensing from the 1 hour fast prior to communion, for example. As such, a “just and reasonable cause” will be judged against the weight of the law.
Second, the priest must only grant dispensations in accord with the diocesan Bishop’s own mind on the subject—making the Bishop’s own decision one that the priests, his “co-workers,” ought to follow. For dispensations from Mass, pastors of parishes do have the faculty to grant them by the law itself; however, other priests (associate pastors) are given this faculty by the bishop to be able to grant dispensations from the obligation to participate in a Sunday or Holy Day Mass to any of their own parishioners who may request such for a reasonable cause.
Finally, dispensations are meant to be granted only in “individual cases;” that is, in a case by case manner—whether it pertains to only one person or several, or
perhaps, even a whole parish if there is a common circumstance the effects the entire parish, for example. Practically speaking then, what are those cases? One possible case might be a sudden circumstance in which a priest is unavailable (in which a whole parish would be dispensed). Another may be a situation in which a person learns in advance of a weekend that they may not be able to participate in Mass, due to circumstances that are beyond their own control.
In applying the law, it is noteworthy that when a priest grants a person a dispensation, he may ask the person to participate in some additional form of prayer within their means to accomplish (such as spending 10-15 minutes in prayer with the readings for that day). Please note that such an act does not substitute for the
obligation; it is simply a means toward helping one carry out a least some act of prayer (even if minimal) beyond what they may normally do.
While such dispensations are meant to be rare, it is important that if you believe you have a just reason that may prevent you from participating in a Sunday or Holy Day Mass that you make the request (acknowledging that a reasonable effort should still be made to participate, even if a dispensation were granted) so that you can
remain in a state of grace and not have any concerns as to whether or not you have a reasonable situation to miss Mass.