The economy of the Middle Ages has been studied (here, for example: http://www.dartmouth.edu/~mkohn/orgins.html), and it had one distinguishing feature: there was no small coinage; the smallest denomination that people would generally accept was a day's wage.
One can guess how people dealt with this: they extended credit to each other. A village's general store served as its bank. Tools and workmen's boots had to be ultra-reliable. In generally, the economy back then looked surprisingly modern (Cicero talks about letters of credit in his letters, the risk in long-distance trade was spread by buying shares in a voyage), the only thing that was missing was advertising.
Was credit something extended to peasants though? It seems like that would mainly apply to people with some wealth or assets to back the credit up. I'm mostly interested in the complete bottom of the rung of society and how they managed in those environments.
I'm not a historian, but the bottom class seems toke a lot of debt. That's a common way for a free man to become a slave. Also, debt relieve (or the lack of) was always a big reason for mass movements or riots.
As for peasants, I'm not sure about Europe, but in China they are one of the biggest client group. They would take out loans in planting season and pay it back in harvest. The standardization of these loans' terms and making it a government monopoly is a big part of Wang Anshi's[1] reform.
It would be more an extended-family or small social scene kind of credit. You know Bob. Every week he buys ale from you. Some weeks he doesn't have cash on the nail. So you let him pay next week. It's not like he's going to run off and you know where he lives. This is a kind of credit, although with bookkeeping no more complicated than a slate (hence the "clean slate" idiom).
One can guess how people dealt with this: they extended credit to each other. A village's general store served as its bank. Tools and workmen's boots had to be ultra-reliable. In generally, the economy back then looked surprisingly modern (Cicero talks about letters of credit in his letters, the risk in long-distance trade was spread by buying shares in a voyage), the only thing that was missing was advertising.