For tax allocation, the principle was to divide the total amount required to be collected by the number of fires, which necessitated a census of fires which was called "réel". The task was relatively simple to perform to the level of an urban district, however it took on a whole different scale in a rural area or across a kingdom. Thus, the king of France only made a single fire census in his territory – in 1328. Yet the result was incomplete as it excluded the great fiefs (e.g.
Guyenne and
Flanders) and some
Appanages. In addition, it became quickly outdated due to the
Black Death. In 1426, the
duke of Brittany made a "reformation of taxes" to limit exemptions (noble families had to prove their nobility) in all the provinces. There were no records of fires by urban community or territorial division (
bailliage or
sénéchaussée in France). Yet their accuracy should be put in perspective: the provinces did not stop asking the central government for revisions, always for reduction, due to famine or epidemic. The total number of fires was therefore subject to hard bargaining between the central government and municipalities, regardless of the reality on the ground. In addition, the poorest families were grouped at the parish level as a single fire for joint taxation. This led to rounded off counts cut off from reality. The "feu fiscal" became a purely theoretical unit, as distinguished from the "feu allumant" (fire lights) which corresponded to the family home. Its value varied depending on the year or on social status even within the same city. It could even be set arbitrarily. Thus, in 1426, the
duke of Brittany decreed that a "fire" corresponded to three "estagiers" (heads of households). The
Taille roles were updated regularly during "visites de feu" (fire visits). ==Their Use and historical demography==