This book describes the construction of algebraic models which represent the operations of the double entry accounting system. It gives a novel, comprehensive, proof based treatment of the topic, using such concepts from abstract algebra as automata, digraphs, monoids and quotient structures. Summary: Interesting applied abstract algebra Rating: 5 Very interesting! The authors show how to apply the abstract algebra to the double-entry accounting, connecting the purest pure math to the common bean-counting chores in Finance. Abstract Algebra is articulate in the description of a formal system, based on a set of axioms and proved theorems. Here, the accounting system is defined as a formal system with 10 axioms. It applies the following abstract algebra concepts: 1) Balance Vector: a single column vector of accounting elements, with total sum zero (balanced account). Debit has '-' sign and Credit '+' 2) DiGraph: Graph with vertices as accounts, edges as transaction. 3) Monoid 4) Automaton 5) homomorphism 6) Quotient group structure