# Metering and Charging

> Charging model for Document Understanding REST API calls, covering both modern and classic project types under Unified Pricing and Flex Plan.

This page describes how Document Understanding REST API calls are charged. Charging depends on the project type (modern or classic) and the licensing model (Unified Pricing or Flex Plan).

For pricing through activity packages (`DocumentUnderstanding.Activities` and `IntelligentOCR.Activities`), see the user-guide pages instead:

- [Metering and charging logic (Unified Pricing)](https://docs.uipath.com/document-understanding/automation-cloud/latest/user-guide/metering-and-charging-logic-unified-pricing) — modern projects under Unified Pricing.
- [Metering and charging logic (Flex Plan)](https://docs.uipath.com/document-understanding/automation-cloud/latest/user-guide/metering-charging-logic) — modern projects under Flex Plan.
- [Metering and charging logic (Classic)](https://docs.uipath.com/document-understanding/automation-cloud/latest/classic-user-guide/metering-charging-logic) — classic projects (activity-based rates).

## Modern projects via API

How Document Understanding modern project REST API calls are charged depends on your licensing model.

### Flex Plan

REST API calls are charged per operation. You pay only for the operations you call on each page:

| Operation | AI units per page |
| --- | --- |
| Digitization (including OCR) | 0 |
| Classification | 0.2 |
| Extraction (with prior classification) | 0.8 |
| Extraction (without prior classification) | 1 |

A page that is both classified and extracted is capped at 1 AI unit total. If you call multiple extractors on the same page, each extraction is charged separately.

:::note
Validation through the API does not consume AI units. **Generative Validation** is a separate feature, and consumes an additional 1 AI unit per page.
:::

### Unified Pricing

REST API calls are charged per operation. You pay only for the operations you call on each page:

| Operation | Platform Units per page |
| --- | --- |
| Digitization (including OCR) | 0 |
| Classification | 0.04 |
| Extraction (with prior classification) | 0.16 |
| Extraction (without prior classification) | 0.2 |

A page that is both classified and extracted is capped at 0.2 Platform Units total. If you call multiple extractors on the same page, each extraction is charged separately.

Calling multiple operations with the same model does not multiply the charge, whereas calling multiple operations with different models multiplies the charge.

:::note
Validation through the API does not consume Platform Units. **Generative Validation** is a separate feature, and consumes an additional 0.2 Platform Units per page.
:::

## Classic projects via API

For Document Understanding classic projects, REST API calls are charged per capability:

| Capability | Unified Pricing | Flex Plan |
| --- | --- | --- |
| Digitization | 0.04 Platform Units/page | 0.2 AI units/page |
| Extraction | 0.2 Platform Units/page | 1 AI unit/page |
| Classification | Applicable per page range — see the table below | Applicable per page range — see the table below |

The consumption for Classification is applicable per page range:

| **Document pages** | **Unified Pricing** | **Flex Plan** |
| --- | --- | --- |
| 1-25 | 0 PU | 0 AIU |
| 26-50 | 0.2 PU | 1 AIU |
| 51-75 | 0.4 PU | 2 AIU |
| 76-100 | 0.6 PU | 3 AIU |
| 101-125 | 0.8 PU | 4 AIU |
| 125+ | 1 PU | 5 AIU |

:::note
Classification charges are capped at a maximum of 1 Platform Unit (or 5 AI units) per document.
:::

For more information on licensing, see the [About licensing](https://docs.uipath.com/automation-cloud/docs/about-licensing) page in the Automation Cloud guide.