This article explores the world of informal financial transactions and informal networks in pre-industrial France. Often considered merely as simple daily transactions made to palliate a lack of cash in circulation and to smooth consumption, the examination of private transactions reveals not only that they served various purposes, including productive investments, but also that they proved to be dynamic. The debts they incurred helped to smooth consumption but also helped to make investments. Some lenders were more prominent than others, although no one really dominated the informal market. This article also compares informal transactions with formal ones through the study of probate inventories and notarial records respectively. It compares these two credit circuits, their similarities and different characteristics, and their various networks features. The debts incurred in the notarial credit market were more substantial but did not serve a different purpose than in the informal market. Here too, the biggest lenders did not monopolise the extension of capital. Perhaps the most striking result lies in the fact that the total volume of exchange between the informal credit market and the notarial credit market (after projection) was similar.