---
title: Balance and purchases
description: Top-ups, your rate, how a purchase is priced, and what happens to the balance.
sidebar:
  order: 5
---

## Top-ups

Top up on the [developer page](https://trimcarbon.com/developers/access), through Stripe Checkout. Each top-up is $250 to $10,000, and the balance can't go above $50,000. For larger amounts, contact us: we can invoice you.

You get an invoice for each top-up. The money becomes balance as soon as Stripe confirms the payment.

## Your rate

Your rate is a price per kg of CO₂, shown on the developer page and in `GET /balance` as `rate_millicents_per_kg` (thousandths of a cent): `4000` is $0.04 per kg, or $40 per tonne.

## How a purchase is priced

- **By volume:** `{"kg": 1000}` costs `kg × rate`, rounded to the cent. At $0.04/kg that's $40.00.
- **By price:** `{"amount_cents": 5000}` buys the most whole kg whose cost fits in the amount, and charges that cost, never more than the amount. At $0.035/kg, $50.00 buys 1,428 kg for $49.98.

Use `POST /quotes` to see both numbers before you buy.

A purchase that the balance doesn't cover fails with `402 insufficient_balance`; nothing is bought. The error tells you the balance and the cost.

## Large purchases

Each account has a review limit, 15 t by default. A purchase above it is accepted and paid from the balance, but waits for our review before the credits are retired. `POST /quotes` tells you with `requires_review`.

## If an order can't be placed

We retry failed orders for you. If one still can't be placed, we return its cost to your balance, and the offset becomes `refunded`.

## Low balance email

Set a threshold on the developer page. We email you once when a purchase takes the balance below it. After a top-up lifts the balance above the threshold, the next drop below it emails you again.

## Terms

The balance is prepaid and **not refundable**. It does not expire. It can only pay for API purchases, and you lose it if you delete your account. The [terms](https://trimcarbon.com/legal/terms-and-conditions#api) have the details.