[Morthoron]

Tolkien did not do commerce very well; in fact, he merely ignored it unless it served a specific purpose to move the story along (the barrel trade with Laketown, for instance, where there is no mention of what the Elves could use in trade/barter/currency).

The Shire and Bree are even more of an anomaly. Considering the last King of Arthedain perished nearly 1000 years previously, it seems incredible that there would be any Dunedain coinage remaining from that time period. Likewise, the Shire had no trade south to Gondor, therefore it seems unlikely that the tharni and castar coins minted in Minas Tirith would have made their way up the Greenway in an amount necessary to be used as everyday coinage.

So, how were deeds and other legal transactions processed? Who paid for the postal service and bounders (as taxation was never mentioned)? No pawn shops or usury (an age-old practice in the real world), no banks -- but, amusingly, there were lawyers (Messrs Grubb, Grubb and Burrowes).

Much like commodes and outhouses, Tolkien simply did not go into detail; otherwise, he would need a many-paged treatise explaining trade, finance, numismatics and global economics. Considering the numerous problems with his personal finances, it is my opinion that Tolkien wanted to stay as far away as possible from the dread realities of finance, even in a fantasy.