---
title: "Add funds and turn on auto top-up"
description: "Pay-as-you-go billing: add a card, load your balance, and set auto top-up so a call never dies mid-sentence."
---

Every new account includes **$10 of free call credit** in its first
organization, with no credit card required. Organizations you add later start
without it. The credit pays for any call: browser tests, phone calls, SIP
calls, web and widget calls, and simulations. Calls use the credit first, then
your cash balance. It cannot pay for phone numbers or voice samples, so add
funds with a card when you want a number.


ThunderPhone billing is pay-as-you-go: calls draw from your
organization's balance at your agent's per-minute rate. No
subscriptions, no seats. Everything on this page lives under
**Organization → Billing Settings**.

## 1. Add a card

A card unlocks top-ups and phone numbers. It's only charged when you
add funds — **never automatically** (unless you later opt into auto
top-up).

## 2. Load your balance

Click one of the preset amounts ($25–$1000) or enter your own, then
**Add to balance** — a confirmation dialog shows exactly what you're
about to charge before you click **Confirm and charge**. Add at least
**$3.00** to start making real calls. Funds never expire.

<Note>
  What a minute costs depends on the agent: engine tier plus
  surcharges (for example, selected
  [premium languages](/guides/supported-languages) and premium voices —
  marked in the voice picker — use a voice/language path of up to
  {/* rate:language */}3¢/min{/* /rate */}). The
  agent builder shows each agent's all-in rate live. Running
  [outbound campaigns](/guides/outbound-campaigns)? Every campaign
  call draws from this same balance, so size your top-ups (or auto
  top-up) to the list you're dialing. Widget `context` is truncated at
  12,000 characters and counts toward prompt-size pricing.
</Note>

## 3. Turn on auto top-up (optional, recommended)

When the balance is about to run out mid-call, the agent is told to
apologize, wrap up, and say goodbye, and the call ends once it is spent.
Auto top-up prevents that from ever happening:

<Steps>
  <Step title="Enable the switch">
    Flip **Enable auto top-up**.
  </Step>
  <Step title="Set the trigger and refill">
    Choose **When balance falls below** (the threshold) and **Add
    amount** (the refill). When the balance dips under the threshold,
    ThunderPhone charges your card for the refill amount.
  </Step>
  <Step title="Optionally cap the month">
    Check **Monthly spending limit** to bound how much auto top-up can
    spend per calendar month.
  </Step>
  <Step title="Save">
    Click **Save changes**.
  </Step>
</Steps>

## Prompt-size surcharge

{/* rate:prompt */}

Per-minute call rates cover agent prompts up to 5,000 tokens. Larger
prompts add a per-minute surcharge: each additional block of 10,000
tokens (or part of one) adds **+1¢/min** on Spark and **+2¢/min** on
Bolt and Storm.

{/* /rate */}

The surcharge is computed from the prompt actually used on each call.
That includes page `context` supplied by an embedded
[web widget](/guides/embed-web-widget), which is capped at 12,000
characters (roughly 3,400 tokens of typical English text). The prompt
editor in the dashboard shows a live estimate while you edit, and each
call's billing-history entry breaks out widget-context tokens.

The complete pricing reference — base tiers, acknowledgements, extra
intelligence, supervision, call metering, hold time, voicemail, simulations,
and phone numbers — is at [ThunderPhone pricing](/guides/pricing).

## Watch the money

The **Billing History** tab lists every transaction — top-ups
(manual and automatic), per-call usage, and monthly phone-number
charges. The same data is available programmatically via the
[Billing API](/api-reference/billing).

---

## Next steps

<CardGroup cols={2}>
  <Card title="Get a phone number" icon="phone" href="/guides/get-a-phone-number">
    With funds loaded, numbers are a click away.
  </Card>
  <Card title="Billing API reference" icon="code" href="/api-reference/billing">
    Balance, top-ups, auto-reload, and transactions over REST.
  </Card>
  <Card title="Pricing reference" icon="coins" href="/guides/pricing">
    Every base rate, surcharge, metering rule, and one-time charge.
  </Card>
</CardGroup>