One-off invoices

Generate an invoice for one-time or ad-hoc charges that are outside a customer’s regular subscription, and bill one or several add-ons immediately.

Why this matters

Not every charge fits a subscription’s billing cycle: a consulting engagement, a hardware shipment, or a charge for a customer who has no subscription at all. A one-off invoice lets you bill these directly, with invoice lines you compose yourself.

How it works

A one-off invoice is created empty in Draft and On Hold status. You then add one or more invoice lines to it, each with its own billing period, product item (or free-text pricing name), and price. When the invoice is complete, move it to Final manually; the invoice number is generated at that point. See the invoice lifecycle for the status flow.

Creating a one-off invoice

Via API

Create the invoice with POST /v1/invoices, setting type to ONE_OFF:

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curl -X POST https://api.solvimon.com/v1/invoices \
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     -H "X-API-KEY: <apiKey>" \
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     -H "Content-Type: application/json" \
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     -d '{
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  "type": "ONE_OFF",
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  "purchase_order_number": "PO-2026-0042",
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  "customer_id": "cust_AbD3DqausjOYiMNDZY11F"
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}'

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{
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  "object_type": "INVOICE",
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  "id": "invo_LwFkp9AvbstgH5ZZ1Qd4",
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  "purchase_order_number": "PO-2026-0042",
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  "customer_id": "cust_AbD3DqausjOYiMNDZY11F",
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  "status": "DRAFT",
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  "on_hold": true,
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  "type": "ONE_OFF",
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  "created_at": "2026-07-02T10:00:00Z",
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  "updated_at": "2026-07-02T10:00:00Z",
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  "billing_currency": "EUR",
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  "payment_status": "UNPAID",
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  "paid": false
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}

Then add lines with POST /v1/invoices/{id}/add-line. Each line specifies the billing period (start_at/end_at, which can be a single day or an entire period), a product_item_id, or a free-text pricing_name if you don’t want to select an existing product, and the price:

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curl -X POST https://api.solvimon.com/v1/invoices/invo_LwFkp9AvbstgH5ZZ1Qd4/add-line \
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     -H "X-API-KEY: <apiKey>" \
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     -H "Content-Type: application/json" \
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     -d '{
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  "pricing_type": "FLAT",
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  "product_item_id": "prii_IwFkp9Avb6tiH5ZZ1Xf2",
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  "product_item_type": "REVENUE",
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  "start_at": "2026-07-01T00:00:00Z",
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  "end_at": "2026-08-01T00:00:00Z",
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  "pricing_band": {
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    "amount": {
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      "quantity": "150.00",
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      "currency": "EUR"
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    }
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  },
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  "volume": {
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    "number": "1"
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  }
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}'

Remove a line again with POST /v1/invoices/{id}/delete-line.

Via Desk

Go to Invoices > Create one-off invoice:

Fill in the details such as the customer and billing entity. Once you’ve created the invoice, add one or several invoice lines to it:

For each line, click “Add invoice line”, specify the billing period, choose the Product Item or Product Line Item from the dropdown (or provide a free-text pricing name to display on the invoice line instead), and input the price amount. The line then appears on the invoice, with the total amount and tax calculations:

Within the invoice settings you can define additional metadata such as the PO number or values for custom fields, under Settings > Edit invoice info.

Edge cases

• One-off invoices can contain the same product multiple times, with the same or different dates and unit pricing.
• Adding only a product-level line item results in the invoice showing the same product name at both the line and sub-line level.
• Default tax settings defined at the customer and billing entity level are applied to the one-off invoice.
• Discounts and commitments are not applicable to one-off invoices.
• Invoice numbers are generated only once the invoice status has been changed to Final.

See also: Invoice lifecycle, On-demand charges and Correcting invoices.