The present publication continues with the series begun in volumes 76, 82 and 92 of the collection, in this case they are contained the corresponding documents in the years 1366 and 1367 of the reign of Charles II of Navarre (1349-1387), as preserved in the sections on Comptos (Accounts), and loose Papers and Records from the General Archives of Navarre. Over these years, Charles II is completely involved in the conflict that takes place in Castille between Pedro I and Enrique de Trastámara, taking sides at first in favour of Pedro. Carlos, however, soon changed opinions and presented with the promises of the King of Aragon (Pedro IV) he then became an ally of Enrique by allowing the French mercenaries transit through his territory to fight against Pedro I. This conflict is reflected in the documentation presented here, as there are numerous references, above all related to economic expenses that the war has brought about. On the other hand there are also data of great interest for the knowledge of the operation of the kingdom of Navarre in political, economic and administrative matters in a key moment for its territory.