According to Can. 992 [quoted from Code of Canon Law, Latin-English Edition (Washington, D.C.: Canon Law Society of America, 1983)] --- An indulgence is a remission before God of the temporal punishment for sin the guilt of which is already forgiven, which a properly disposed member of the Christian faithful obtains under certain and definite conditions with the help of the Church which, as the minister of redemption, dispenses and applies authoritatively the treasury of the satisfactions of Christ and the saints.

Can. 993 --- An indulgence is partial or plenary in as far as it frees from the temporal punishment due to sin either partly or totally.

Can. 994 --- The faithful can gain partial or plenary indulgences for themselves or apply them for the dead by way of suffrage.

Can. 995 --- 1. Besides supreme authority of the Church, only those can grant indulgences to whom this power has been given by the law or granted by the Roman Pontiff. 2. No authority beneath the Roman Pontiff can commit to others the power to grant indulgences unless it was expressly given by him by the Apostolic See.

Can. 996 --- 1. In order that one be capable of gaining indulgences one must be baptized and not excommunicated and in the state of grace at least at the completion of the prescribed works. 2. In order that one be a capable subject for gaining indulgences one must have at least the intention of receiving them and fulfill the enjoined works at the stated time in due fashion, according to the tenor of the grant.

Can. 997 --- In regard to the granting and use of indulgences other prescriptions contain in the particular laws of the Church must be also observed.

Moreover, the following points or norms are taken from Pope Paul VI's Apostolic Constitution The Doctrine of Indulgences issued on January 1, 1967 (Norm 1-3 have been stated in different words by the Canons above):

Norm 4 --- A partial indulgence will henceforth be designated only with the words 'partial indulgence' without any determination of days or years.

Norm 5 --- The faithful who at least with a contrite heart perform an action to which a partial indulgence is attached obtain, in addition to the remission of temporal punishment acquired by the action itself, an equal remission of punishment through the intervention of the Church.

Norm 6 --- A plenary indulgence can be acquired only once a day, except for provisions contained Norm 18 for those who are on the point of death. A partial indulgence can be acquired more than once a day, unless there is an explicit indication to the contrary.

Norm 7 --- To acquire a plenary indulgence it is necessary to perform the work to which the indulgence is attached and to fulfill three conditions: sacramental confession, Eucharistic Communion and prayer for the intentions of the Supreme Pontiff. It is further required that all attachment to sin, even to venial sin, be absent.

If this disposition is in any way less than complete, or if the prescribed three conditions are not fulfilled, the indulgence will be only partial…

Norm 8 --- The three conditions may be fulfilled several days before or after the performance of the prescribed work; nevertheless it is fitting that Communion be received and the prayers for the intentions of the Supreme Pontiff said the same day the work is performed.

Norm 9 --- A single sacramental confession suffices for gaining several plenary indulgences, but Communion must be received and prayers for the Supreme Pontiff's intentions recited for the gaining of each plenary indulgence.

Norm 10 --- The condition of praying for the Supreme Pontiff's intentions is fully satisfied by reciting one Our Father and one Hail Mary; nevertheless the individual faithful are free to recite any other prayer according to their own piety and devotion toward the Supreme Pontiff.

Norm 18 --- To the faithful in danger of death who cannot be assisted by a priest to bring them the sacraments and impart the apostolic blessing with its attendant plenary indulgence Holy Mother Church nevertheless grants a plenary indulgence to be acquired at the point of death, provided they are properly disposed and have been in the habit of reciting some prayers during their lifetime. To use a crucifix or cross in connection with the acquisition of this plenary indulgence is a laudable practice.

This plenary indulgence at the point of death can be acquired by the faithful even if they have already obtained another plenary indulgence on the same day.

Norm 20 --- Holy Mother Church, extremely solicitous for the faithful departed, has decided that suffrages be applied to them to the widest possible extent at any Sacrifice of the Mass whatsoever, abolishing all special privileges in this regard.

* The above is taken word for word from Enchiridion of Indulgences: Norms and Grants, Authorized English Edition. Translated by William T. Barry, C.SS.R. from the second revised Edition of "Enchiridion Indulgentiarum" issued by the Sacred Apostolic Penitentiary, 1968 (New York: Catholic Book Publishing Co., 1969) [Originally published by Libreria Editrice Vaticana, Vatican City, 1968] pp.108-112.