List expenses, most recent first.

When group_id is omitted, the SPLITWISE_GROUP_ID default is used. Pass group_id=0 to list expenses across all groups and non-group expenses. Date filters (dated_after/before, updated_after/before) accept ISO 8601 strings, e.g. "2026-01-31T00:00:00Z".

Get the full details of a single expense by its id.

Create a new expense.

cost is a decimal string, e.g. "25.00". description is required.

Splitting:

• Equal split (default): leave users empty; the cost is split evenly among everyone in the resolved group (group_id or SPLITWISE_GROUP_ID).

• Custom split: pass users, a list of dicts each like {"user_id": 123, "paid_share": "25.00", "owed_share": "12.50"}. Identify a user by user_id, or by email/first_name/last_name. The paid_share values must sum to cost, and so must the owed_share values.

date accepts ISO 8601 (e.g. "2026-06-15T00:00:00Z"). currency_code is a 3-letter code (e.g. "USD"). category_id and details are optional.

Update an existing expense. Only provided fields are changed.

Note: if you pass users (custom shares), it overwrites ALL existing shares on the expense — include every participant. See create_expense for the users format and split rules.

Delete an expense by id. Returns {"success": true} on success.