According to the Catechism of the Catholic Church, it states clearly that Catholics are bound to confess serious sins at least once a year. But it also notes that “without being strictly necessary, confession of everyday sins (venial sins) is nevertheless strictly recommended by the Church” (CCC 458).
Canon 989 states that all Catholics who have reached the age of reason (traditionally understood to mean roughly the age of seven, which is about the time that most Catholic children make their first confessions) are obliged to confess all mortal sins at least once a year.
But canon 988.2 notes also that it is recommended though not required that Catholics also confess venial sins. It should be obvious that the canons which address this issue are in perfect accord with the Catholic theology.
Firstly, a Catholic is advised to receive a sacrament when he approaches a priest at the time and place where that sacrament is regularly conferred.
We are also advised to receive Holy Communion, for example, when we approach a priest who is distributing Communion during Mass. In the same way we also advised to receive the sacrament of penance by going into the confessional at the time when confessions are regularly held in our parishes.
However, trying to get a priest to hear confessions while in a movie theater, or at 2 AM, is not advisable and a priest may justly refuse such a request. Only in the case of a dying person, in which the person has the right to the sacraments no matter where he is or what time it is.
Moreover, there are many possible reasons why a Catholic may be by law prohibited from receiving a sacrament. If, for instance, the person is under excommunication, he is forbidden to receive the sacraments until the excommunication is lifted (Can. 1331.1 n. 2 ).
Or, if the faithful simply be too young to receive a particular sacrament. If the sacrament may be received only once (as is the case with baptism, confirmation, or holy orders), a Catholic who has already received it once may not receive it again.
Or there may be an obstacle barring a person’s reception of a sacrament. A Catholic may not receive the sacrament of matrimony, if for instance, he is in holy orders, or is already married to someone else.
Based on any of the above cases, a priest may deny a faithful of a particular Sacrament.