> ## Documentation Index
> Fetch the complete documentation index at: https://docs.nomos.energy/llms.txt
> Use this file to discover all available pages before exploring further.

# Checkout

> Take a customer from quote to active subscription using your own UI, with Nomos handling the contract, supplier switch, and billing in the background.

A custom checkout takes a customer from quote to active subscription with three calls. Nomos handles the rest: cancelling the old contract, registering with the grid operator, starting billing. Every call runs from your backend.

## How it works

<Steps>
  <Step title="Quote">
    [Retrieve a quote](/api-reference/plans/retrieve-a-quote) with the plan,
    zip code, and expected usage. The response includes the working price
    (`Arbeitspreis`) and basic price (`Grundpreis`), broken down so you can
    render a transparent estimate. For a layer-by-layer walkthrough of each
    component, see [Pricing breakdown](/guides/pricing).

    <Tip>
      If you don't yet know the customer's expected usage, ask them how many
      people live in the household. 1 person ≈ 1500 kWh, 2 ≈ 2500, 4 ≈ 4500.
    </Tip>
  </Step>

  <Step title="Resolve the previous supplier">
    Pick the previous supplier from the directory using [List market
    partners](/api-reference/market-partners/list-market-partners). Filter by
    `name` for autocomplete, or fetch the full list for a static dropdown.
    Store the `id`; you'll send it back at submission. For move-ins, omit
    `previous_supplier` entirely.
  </Step>

  <Step title="Create the subscription">
    POST to [Create a
    subscription](/api-reference/subscriptions/create-a-subscription) with
    `plan`, `customer`, `address`, `meter`, `payment_method`, and
    `previous_supplier`. To enable smart-meter rollout or §14a EnWG modules in
    the same call, include a `product_orders` array; see [Smart
    meters](/guides/order-smart-meters) and [§14a grid fee
    reductions](/guides/grid-fee-reductions). The response contains the new
    `subscription.id`; store it for invoices, prices, meter readings, and
    status changes.
  </Step>
</Steps>

## FAQ

<AccordionGroup>
  <Accordion title="What's the minimum I need to ship?">
    Quote, supplier search, and the create call. Address validation,
    plausibility checks, and IBAN formatting can come from your existing
    libraries; everything else, Nomos handles after `subscription.created`.
  </Accordion>

  <Accordion title="How do I know when the supplier switch actually goes through?">
    Two webhooks tell the story.
    [`subscription.created`](/webhooks/events/subscription-created) fires
    immediately on creation; use it to provision your own user record.
    [`subscription.confirmed`](/webhooks/events/subscription-confirmed) fires
    once the grid operator accepts the switch, typically 2 to 3 weeks later; use
    it for confirmation emails and to unlock portal access.
  </Accordion>

  <Accordion title="What's the difference between a move-in and a supplier switch?">
    A supplier switch (Lieferantenwechsel) replaces an existing contract: pass
    the previous supplier's `id` in `previous_supplier`, and Nomos cancels the
    old contract and handles the handover with the grid operator. A move-in
    (Einzug) is a fresh signup with no prior contract: omit `previous_supplier`
    entirely. Switches respect the existing contract's notice period; move-ins
    can start as early as the move-in date itself.
  </Accordion>
</AccordionGroup>