abacus

A minimal, yet valid double-entry accounting system, provided as abacus-py Python package and the bx command line tool.

Using abacus you can:

• define a chart of accounts,
• post regular and adjustment entries to ledger,
• make trial balance,
• close accounts at period end,
• produce balance sheet and income statement.

Quotes about abacus

I think it's a great idea to mock-up a mini GL ERP to really get a foundational understanding of how the accounting in ERP works!

I teach accounting information systems... I'd be tempted to use abacus as a way of simply showing the structure of a simple AIS.

Hey, what a cool job, thanks much. Do you plan to make a possibility for RAS accounting?

Install

pip install abacus-py

This will install both abacus-py package and the bx command line tool.

For latest version install from github:

pip install git+https://github.com/epogrebnyak/abacus.git

abacus-py requires Python 3.10 or higher.

Minimal command line example

Сreate temporary directory where chart.json and entries.csv will be created:

mkdir -p scripts/try && cd scripts/try

Create chart of accounts:

bx chart init
bx chart add --asset cash
bx chart add --asset ar --title "Accounts receivable"
bx chart add --asset goods --title "Inventory (goods for resale)"
bx chart add --asset prepaid_rent --title "Storage facility prepaid rent"
bx chart add --capital equity
bx chart add --liability dividend_due
bx chart add --income sales
bx chart offset sales discounts
bx chart add --expense cogs --title "Cost of goods sold"
bx chart add --expense sga --title "Selling, general and adm. expenses"
bx chart alias --operation invoice --debit ar --credit sales
bx chart alias --operation cost --debit cogs --credit goods
bx chart show

Start ledger, post entries and close accounts at period end:

bx ledger init
bx ledger post entry --debit cash  --credit equity --amount 5000 --title "Initial investment"
bx ledger post entry --debit goods --credit cash   --amount 3500 --title "Acquire goods for cash"
bx ledger post entry --debit prepaid_rent --credit cash --amount 1200 --title "Prepay rent"
bx ledger post operation invoice 4300 cost 2500 --title "Issue invoice and register sales"
bx ledger post entry --debit discounts --credit ar --amount  450 --title "Provide discount"
bx ledger post entry --debit cash  --credit ar     --amount 3000 --title "Accept payment"
bx ledger post entry --debit sga   --credit cash   --amount  300 --title "Reimburse sales team"
bx ledger post entry --debit sga --credit prepaid_rent --amount 800 --title "Expense 8 months of rent" --adjust
bx ledger close
bx ledger post entry --debit re --credit dividend_due --amount 150 --title "Accrue dividend" --after-close

Make reports:

bx report --trial-balance
bx report --balance-sheet
bx report --income-statement

Inspect accounts:

bx account sales
bx assert cash 3000
bx balances --nonzero

The results should look similar to this:

Balance sheet
Assets                          5500  Capital              5500
- Cash                          2700  - Equity             5000
- Accounts receivable           1500  - Retained earnings   500
- Inventory (goods for resale)  1300  Liabilities             0
Total                           5500  Total                5500

Income statement
Income                                                     3500
- Sales                                                    3500
Expenses                                                   3000
- Cost of goods sold                                       2700
- Selling, general and adm. expenses                        300
Profit                                                      500

from abacus import Chart, Entry, BalanceSheet, IncomeStatement

chart = (
    Chart(
        assets=["cash", "ar", "goods"],
        expenses=["cogs", "sga"],
        equity=["equity", "re"],
        income=["sales"],
    )
    .offset("sales", "discounts")
    .set_name("cogs", "Cost of goods sold")
    .set_name("sga", "Selling, general and adm.expenses")
    .set_name("goods", "Inventory (goods for sale)")
    .set_name("ar", "Accounts receivable")
)

ledger = (
    chart.ledger()
    .post(Entry(debit="cash", credit="equity", amount=1000))
    .post(Entry(debit="goods", credit="cash", amount=800))
    .post(Entry(debit="ar", credit="sales", amount=465))
    .post(Entry(debit="discounts", credit="ar", amount=65))
    .post(Entry(debit="cogs", credit="goods", amount=200))
    .post(Entry(debit="sga", credit="cash", amount=100))
    .post(Entry(debit="cash", credit="ar", amount=360))
)

income_statement = ledger.income_statement(chart)
income_statement.print(chart.names)
income_statement.print_rich(chart.names)
assert income_statement == IncomeStatement(
    income={"sales": 400}, expenses={"cogs": 200, "sga": 100}
)

ledger.close(chart)
balance_sheet = ledger.balance_sheet(chart)
balance_sheet.print(chart.names)
balance_sheet.print_rich(chart.names)
assert balance_sheet == BalanceSheet(
    assets={"cash": 460, "ar": 40, "goods": 600},
    capital={"equity": 1000, "re": 100},
    liabilities={},
)

# Create end of period balances
end_balances = ledger.nonzero_balances()
print(end_balances)
next_book = chart.ledger(starting_balances=end_balances)

Documentation

https://epogrebnyak.github.io/abacus/

Feedback

Anything missing in abacus? Got a good use case for abacus or used abacus for teaching?

Feel free to contact abacus author in issues, on reddit or via Telegram.

Your feedback is highly appreciated and should help steering abacus development.

Contributions

Program design

abacus is designed around core accounting concepts such as chart of accounts, general ledger, accounting entry and financial reports. These concepts correspond to classes created inside abacus: Chart, Ledger, Entry, BalanceSheet and IncomeStatement.

Here is a basic workflow how these classes interact:

• you add necessary accounts to Chart indicating account type,
• from Chart you create empty Ledger,
• an Entry or a list of entries [Entry] can be posted to Ledger,
• there is a procedure to create a list of closing entries and these closing entries are also posted to ledger;
• from Ledger you can get account balances;
• the account balances are used to create trial balance, BalanceSheet and IncomeStatement.

As seen in the code in README, you can use just abacus.Chart and abacus.Entry classes to write code for the entire accounting cycle as other classes (Ledger, balances, BalanceSheet and IncomeStatement) will be derived form Chart and Entry.

In the sequence above the most tricky part are probably the closing entries, thus special care is given to documenting them in the abacus.closing module.

Handling contra accounts also required some thinking to implement, but I believe we have contra accounts nicely covered in the abacus type system (there is a contra account class for each account class, e.g. Asset and ContraAsset).

Fro storage of data we persist the chart and the entries and we do not save the state of the ledger. Given the chart (from chart.json file) and accounting entries (from the entries.json file) we can calculate ledger state at any time. This may seem a bit counter-intuitive, but think of entries as deltas to the original state of the ledger.

If you into functional programming, the entire type signature for abacus is the following:

Chart -> [Entry] -> Ledger -> [ClosingEntry] -> Ledger -> (BalanceSheet, IncomeStatement)

In general, what abacus (as well as any other double entry program) does is maintaining an extended accounting equation in balance. If you are comfortable with this idea, the rest of program flow and code should be more natural to follow.

Note that "real" ERP and accounting systems do a lot more than double entry accounting, for example keeping the original documents and maintaining identities for the clients and suppliers as well as keeping extra data about contracts and whatever management accounting may need to have a record of. Validating and invalidating entries is also a common task.

Most of this of this is out of scope for double entry ledger. We just need a chart of accounts, create a ledger based on chart, post entries that have information about debit, credit and amount, close ledger at period end and produce reports, plus allow checking the trail balance and doing adjustment and post-close entries if needed.

Testing

You will need just command runner and poetry package manager for developing abacus.

All commands I use for testing are gathered in just grill command. This command will launch:

• pytest for unit tests
• mypy to check type annotations
• isort to sort imports
• black for code formatting
• ruff for code check and linting
• prettier to clean markdown files
• console scripts and Python code from README to keep README up to date
• bash scripts with command line interface commands as additional tests.

I found that testing CLI with a few bash files, each for chart, ledger, reports and show commands, accelerates the workflow.