I could examine whether the conquered Gauls and Romans continued to pay the charges to which they were subjected under the emperors. But to expedite things, I will be content to say that if they paid them at first, they were soon exempted, and that those tributes were changed to military service ; and I admit that I can scarcely see how the Franks would first have been so friendly to extortion, and then suddenly appeared so adverse to it.
A capitulary of Louis the Debonaire  explains very well to us the state of free men in the Frankish monarchy. A few bands  of Goths or Iberians fleeing the oppression of the Moors were allowed onto the lands of Louis. The convention that was made with them states that, like the other free men, they would go to the army with their count ; that on the march they would mount the guard and patrols  under the orders of the selfsame count, and supply to the king’s envoys and to ambassadors who came from his court, or were going to him,  horses and wagons for transport ; that otherwise they could not be obliged to pay any other cens, and that they would be treated as the other free men.
We cannot say that these were new practices introduced early in the second dynasty ; all that must belong at least to the middle or end of the first. A capitulary of the year 864  states expressly that it was an ancient custom for free men to do military service and pay in addition for the horses and wagons which we have mentioned, charges that were specific to them, from which people who possessed fiefs were exempt, as I shall prove in what follows.
What is more, there was a statute that did not at all allow subjecting these free men to tributes.  A man who had four manors  was always obligated to march to war ; he who only had three was paired with a free man who only had one : the latter defrayed him for a quarter of the expenses and stayed home. Likewise, two free men who had two manors each were paired ; the one who marched had half his expenses defrayed by the one who stayed.
Moreover, we have an infinite number of charters where privileges of fiefs are given to parcels of land or districts owned by free men, which I shall discuss further on. These holdings are exempted from all the charges that the counts and other officers of the king imposed on them ; and as all these charges are specifically enumerated, and there is no mention of tributes, it is clear that none were levied.
Roman tax extortion very simply disappeared of its own accord in the Frankish monarchy ; it was a very complex art, which entered into neither the notions nor the plan of those simple peoples. If the Tartars inundated Europe today, it would take a lot of doing to make them understand what is meant here by a financier.
The uncertain author of the life of Louis the Debonaire, speaking of the counts and other officers of the Frankish nation which Charlemagne established in Aquitaine, says he assigned them the border guard, the military power, and the intendency of the domains belonging to the crown.  That fact shows the state of the prince’s revenues in the second dynasty. The prince had kept the domains, which he had his slaves exploit. But the declarations, the capitation, and other taxes levied in the time of the emperors on the person or property of free men had been changed into an obligation to guard the border or go to war.
The bishops writing to Louis, brother of Charles the Bald, said to him : “Take care of your lands, so you will not be obliged by the houses of the ecclesiastics to travel endlessly and fatigue their serfs with wagons. Do what is needed,” they further said, “so you will have enough to live on and to receive embassies.”  It is visible that the kings’ revenues then consisted in their domains.