The cassock obligatory for cardinals and bishops during office hours. Cassock or clerical dress for priests and monsignors. Specific habit for religious, always and in every season. And for ceremonies in the presence of the pope or during official meetings in the Roman curia: "abito piano," or cassock with cape, for priests, embroidered cassock for monsignors, and cassock with embroidered cape (called a "pellegrina") for bishops and cardinals.
You can read the entire piece there, but here is the actual note from Cardinal Bertone:
From the Vatican, October 15, 2012
Most Reverend Eminence/Excellency,
by these presents I wish to recall to Your attention the importance of the discipline concerning the daily use of ecclesiastical (cassock or clerical) and religious dress, as determined by the norms on this matter and according to the reasons illustrated and explicated in his day by Blessed John Paul II in the Letter to the Cardinal Vicar of Rome, dated September 8, 1982.
At a time in which everyone is specially called to renew his awareness of and consistency with his own identity, at venerable behest I come to ask Your Eminence/Excellency kindly to guarantee the observance of the above on the part of all ecclesiastics and religious in service with this Dicastery/Tribunal/Office/Vicariate, recalling the duty of wearing regularly and with dignity the proper habit, in every season, partly in obedience to the duty of exemplarity (editor's note: this phrase is in italics in the original) that is incumbent above all upon those who render service to the successor of Peter.
The very example of those who, sealed with the episcopal dignity, are faithful to the daily use of the cassock proper to them, during office hours, becomes an explicit encouragement for all, including for the Episcopates and for those who visit the Roman Curia and Vatican City.
On this occasion, moreover, partly in order to avoid uncertainty and to guarantee due uniformity, it should be recalled that the use of the abito piano is required for participation at any event at which the Holy Father is present, as also for the Plenary and Ordinary Assemblies, the Interdicasterial Meetings, the reception of "ad limina" Visits and the various official engagements of the Holy See.
Grateful for the cooperation, I gladly take this opportunity to confirm my distinct and heartfelt respects
for Your Most Reverend Eminence/Excellency
most devoted in the Lord
+ Tarcisio Card. Bertone
Secretary of State