# High-precision pricing

Most prices fit neatly into the smallest unit of a currency: cents, for AUD or USD. B2B breaks that assumption. A distributor selling cabling, chemicals, or fasteners may price at a fraction of a cent per unit, then multiply by thousands of units per Line Item. If you store such a price rounded to the nearest cent, the rounding error multiplies with the quantity and the invoice total drifts. High-precision pricing exists for exactly this case.

## Cent precision versus high precision

commercetools represents money in one of two forms:

- **`CentPrecisionMoney`** stores an amount in the currency's standard minor units. For AUD, `centAmount` 129900 is AUD 1,299.00. This is the default and the right choice for almost all prices.
- **`HighPrecisionMoney`** stores an amount as a fraction of the smallest indivisible unit, allowing more decimal places than the currency normally has. You use it when a per-unit price genuinely needs sub-cent accuracy.

`HighPrecisionMoney` uses `preciseAmount` and `fractionDigits` to represent sub-cent values. See [HighPrecisionMoney](/urn?urn=ctp%3Aapi%3Atype%3AHighPrecisionMoney) for field constraints.

For example, to price a component at AUD 0.012345 each, you set `fractionDigits` to 6 and `preciseAmount` to 12345; that is, 12345 / 10^6 = 0.012345.

```http
POST /{projectKey}/standalone-prices HTTP/1.1
Content-Type: application/json

{
  "sku": "ZET-CABLE-CAT6-METER",
  "channel": { "typeId": "channel", "key": "atlas-apac-pricing" },
  "value": {
    "type": "highPrecision",
    "currencyCode": "AUD",
    "preciseAmount": 12345,
    "fractionDigits": 6
  }
}
```

`fractionDigits` and the size of the integer part trade off against each other. `preciseAmount` is a 64-bit integer, so the more decimal places you reserve with `fractionDigits`, the smaller the maximum whole-currency amount you can represent. Choose the smallest `fractionDigits` that captures the precision your contract needs, rather than the maximum.

## Rounding happens at the Cart

A high-precision unit price has to become a payable amount somewhere. That rounding is governed by the Cart's `priceRoundingMode`, which applies when a Line Item's price uses `HighPrecisionMoney`. The Cart's `priceRoundingMode` uses [RoundingMode](/urn?urn=ctp%3Aapi%3Atype%3ARoundingMode). For B2B invoices with many high-quantity lines, `HalfEven` is usually the safest default because it minimizes cumulative rounding bias. Choose another rounding mode only when a specific invoicing or regulatory requirement calls for it.

## Worked example: an Atlas Corporate bulk order

Atlas Corporate's APAC division orders 12,500 meters of Cat6 cable priced at AUD 0.012345 per meter.

- The unit price is stored as `preciseAmount` 12345 with `fractionDigits` 6.
- The raw Line Item total is 12,500 × 0.012345 = AUD 154.3125.
- With `priceRoundingMode: HalfEven`, the payable Line Item total rounds to **AUD 154.31** (the third decimal, 2, rounds down).

Now compare the alternative: if the price had been stored as `CentPrecisionMoney` rounded to AUD 0.01 per meter, the Line Item would total 12,500 × 0.01 = AUD 125.00, an error of nearly AUD 30 on a single line, growing with every additional unit. High precision keeps the per-unit accuracy and defers a single rounding to the payable total, which is what a bulk B2B invoice requires.

## Key takeaways

- Use `CentPrecisionMoney` for ordinary prices; reach for `HighPrecisionMoney` only when a per-unit price needs sub-cent accuracy that multiplies across large quantities.
- `HighPrecisionMoney` pairs `preciseAmount` with `fractionDigits` to store sub-cent values; check the API reference for field constraints.
- Because `preciseAmount` is a 64-bit integer, more decimal places means a smaller maximum integer amount; use the smallest precision the contract needs.
- The Cart's `priceRoundingMode` decides how a high-precision price becomes payable; use [RoundingMode](/urn?urn=ctp%3Aapi%3Atype%3ARoundingMode) to check the available modes, and use `HalfEven` as the bias-minimizing default for B2B invoicing.

## Related pages

- [Area overview page with navigation](/learning-model-b2b-commerce.md)
- [Previous page: Price versus discount: Channels and Customer Groups](/learning-model-b2b-commerce/configure-b2b-pricing/price-versus-discount.md)
- [Next page: Net prices, gross prices, and tax](/learning-model-b2b-commerce/configure-b2b-pricing/net-and-gross-prices-and-tax.md)