curl -X POST https://api.chargeapi.co/v1/invoices/inv_fn8XLomaZ8hGbUxUx4ATRMaFj6leGAXd/finalize \
  -H "Authorization: Bearer ch_sk_test_..." \
  --json '{}'

{
    "id": "inv_fn8XLomaZ8hGbUxUx4ATRMaFj6leGAXd",
    "object": "invoice",
    "amount_due": 2500,
    "amount_paid": null,
    "created": "2026-05-02T00:38:23.720Z",
    "currency": "eur",
    "description": null,
    "due_date": "2026-05-09T00:38:07.926Z",
    "fleet": "flt_z46UY7MfMuWUxwxHcmCHojeAPdBTbFEm",
    "line_items": [
        {
            "amount": 1842,
            "description": "Charging sessions for March 2026",
            "quantity": 1,
            "unit_amount": 1842
        },
        {
            "amount": 658,
            "description": "Reservation fees",
            "quantity": 2,
            "unit_amount": 329
        }
    ],
    "metadata": {},
    "paid_at": null,
    "payment_method": null,
    "period_end": "2026-05-02T00:37:55.730Z",
    "period_start": "2026-04-01T00:38:04.412Z",
    "status": "open"
}