This study employs Social Network Analysis (SNA) to examine the structure and functioning of the peer-to-peer credit market in the first half of nineteenth-century Milan. By reconstructing over 2200 notarised loan transactions involving more than 1600 unique actors in the years 1825 and 1840, we demonstrate how notaries acted as key intermediaries, reducing reputational risk, facilitating trust-based lending beyond kinship and local ties, and enabling the formation of reliable credit relationships. Despite the market’s sparse topology, the rise in dual-role participants (both lenders and borrowers) and the modest expansion of connected components point to the spread of financial practice. Crucially, the regression results confirm that notaries played a central role in establishing a separating equilibrium, whereby borrower risk was credibly signalled and priced. This mechanism prevented credit rationing and ensured a relatively efficient allocation of capital. As such, the Milanese peer-to-peer credit market proved particularly conducive to economic modernisation, by supporting entrepreneurial initiatives from actors with limited landed collateral but strong reputational standing. The findings reveal a robust and functional non-institutional financial system that underpinned the expansion of productive capital and the emergence of a more dynamic bourgeois economy.