Business Splits

The business split engine automatically allocates a percentage of personal expenses to your business for ATO deduction purposes. This is configured in config/tax.yaml and computed by etl/splitter.py.

How it works

There are two allocation mechanisms:

1. Implicit 100% — Business categories

Any transaction categorised with a name starting with Business: is automatically allocated at 100% to your business:

• Business: Hosting & Infrastructure — hosting, domains, DNS
• Business: Software & Subscriptions — SaaS tools, dev subscriptions
• Business: Equipment — cameras, computers, hardware
• Business: Advertising & Marketing
• Business: Other

No config needed for these — the split engine detects the Business: prefix.

2. Partial allocation — Split rules

Personal expenses that are partially business-use require explicit split rules in config/tax.yaml:

businesses:
  - name: "My Business"
    abn: "00000000000"
    split_rules:
      - category: Utilities
        tag: internet
        business_pct: 50      # 50% of internet bill
      - category: Utilities
        tag: mobile
        business_pct: 20      # 20% of mobile bill

A split rule matches when both conditions are true:

1. The transaction’s category matches category
2. The transaction has a tag matching tag

For example, a Vodafone bill categorised as “Utilities” with tag “mobile” would have 20% allocated as a business expense.

The split pipeline

At ingest time

If tax_config is passed to the normalizer, splits are computed during ingestion:

1. Transaction is categorised and tagged
2. apply_splits() checks if category starts with Business: (100% allocation) or matches a split rule
3. A row is written to transaction_splits with: transaction_id, business_name, business_pct, business_amount

Backfill

More commonly, splits are computed after ingestion using the CLI:

ledger split --backfill --fy 2025

This:

1. Clears all existing splits for the given FY
2. Iterates every non-transfer transaction in the FY date range
3. Loads each transaction’s category and tags
4. Computes splits using the rules from config/tax.yaml
5. Writes results to transaction_splits

Manual override

Individual splits can be overridden via the API:

curl -X PATCH http://localhost:5050/api/transactions/42/split \
  -H "Content-Type: application/json" \
  -d '{"business_pct": 75, "business_name": "My Business"}'

Set business_pct to 0 to remove a split.

Database schema

CREATE TABLE transaction_splits (
    id INTEGER PRIMARY KEY,
    transaction_id INTEGER NOT NULL REFERENCES transactions(id),
    business_name TEXT NOT NULL,
    business_pct REAL NOT NULL,
    business_amount REAL NOT NULL,
    UNIQUE(transaction_id, business_name)
);

A transaction can have splits for multiple businesses (the unique constraint is per business name).

Viewing splits

Dashboard

The Spreadsheet > Outgoing tab shows all expenses with business split columns: percentage, amount, and business name.

API

GET /api/spreadsheet/outgoing?fy=2025 returns each expense transaction with a splits array and convenience fields biz_pct, biz_amount, biz_name.

ATO return

GET /api/ato/return?fy=2025 aggregates splits per business and includes them in the business schedule section with total income, expenses, depreciation, and net profit/loss.

CLI

ledger tax --fy 2025

Prints business expenses from splits, depreciation items, and manual entries.

Tags are essential

Split rules depend on tags to distinguish sub-types within a category. Make sure your config/categories.yaml has tag rules for the relevant patterns:

tag_rules:
  - tag: internet
    pattern: "TPG|SUPERLOOP"
  - tag: mobile
    pattern: "OPTUS|VODAFONE"

Without the correct tags, split rules will not match and the expense will not be allocated.

Example workflow

1. Add a split rule to config/tax.yaml:

   split_rules:
     - category: Utilities
       tag: internet
       business_pct: 50

2. Ensure a tag rule exists in config/categories.yaml:

   tag_rules:
     - tag: internet
       pattern: "TPG|SUPERLOOP"

3. Ingest statements: ledger ingest

4. Backfill splits: ledger split --backfill --fy 2025

5. View results: ledger tax --fy 2025 or check the dashboard Tax tab