This project implements a double-entry accounting system in Clojure which uses an in-memory datascript database for indexing and querying. Data can be imported from Ledger files with a somewhat expanded syntax. Data is persisted as a merkle-dag data structure.
Ledjer organizes financial data into a set of independent books, each of which has a balanced tree of accounts which obey the accounting equation. Books allow for top-level separation, for example tracking your personal finances versus the finances for a club or small business.
Each book has a journal, which is a sequence of transactions, each of which contains one or more entries such as postings. In addition, all books use a shared set of commodity definitions and price history.
A commodity is unit of value exchange, identified by a symbolic code.
Currencies are a kind of commodity, such as USD, EUR, and CNY. Similarly,
each stock is its own commodity, as are shares of ETFs and mutual funds.
Commodities can also be used to represent more esoteric kinds of value, like
airline miles or hours worked.
Over time, a commodity's value may change relative to other commodities. In particular, currencies fluctuate and the values of investments grow and shrink. The conversion rate between two commodities determines the primary commodity's price in the second (or 'base') commodity.
Accounts are named containers for commodities in a set of books. Each account is
identified by a colon-separated path, such as Assets:Cash:Apple Bank:Savings.
This forms a hierarchical tree of accounts, with 'real' accounts at the leaves.
The top-level accounts should generally be the standard 'Assets', 'Liabilities',
'Income', 'Expenses', and 'Equity'.
An account's register is the history of entries applied to it. The register is
ordered by time, and the first entry must be an open-account marker. If
the account has been closed, then the last entry must be a close-account
marker. In between can be notes, balance checks, and postings.
A transaction ties together multiple postings into a balanced unit. The amounts within a transaction MUST sum to zero - this is the fundamental principle of double-entry accounting! A posting represents a change in value for a certain commodity within an account.
A simple transaction could contain two postings, one with an amount of
#finance/$ [5.00M USD] to the account Expenses:Food:Groceries and another
with the inverse amount #finance/$ [-5.00M USD] posted to
Assets:Cash:Wallet. The transaction could have a title like "Grocery Store".
A line item is a detailed breakdown of part of a posting amount. This is like a single line on a receipt from a store: the individual item purchased forms part of the total amount which is posted to the appropriate expense account.
An item may have an amount, which can be a bare number or a physical quantity. The price is the unit price of the item, as either a quantity or a percentage scalar. The item total multiplies the two and takes the commodity specified in the price. This is rendered like so:
$20.18 (2.0 lb @ $10.09)
When the amount is a financial quantity and the price is a regular number, it's considered to be a percentage of the amount. One common example is tax, which is applied as a fraction of the bill total. This is rendered like:
$12.22 ($127.29 @ 9.6%)