# Code sources
URL: https://backworkhealth.com/docs/code-sources

Why each policy code entry has a source, what document and inferred_title_match mean, and how to treat inferred codes

Every code that Backwork links to a policy has a `source`. It says how Backwork knows that the policy covers the code.

| `source`               | Meaning                                                                                                                    |
| ---------------------- | -------------------------------------------------------------------------------------------------------------------------- |
| `document`             | The payer's policy document lists the code.                                                                                |
| `inferred_title_match` | The document does not list the code. Backwork attached it because the policy title names the drug that the code bills for. |

Inferred codes come from drug policies whose documents name the drug but do not list its billing codes.

## Where you see it [#where-you-see-it]

* **API.** Code entries in responses carry `source`, for example each policy in [`lookupCode`](/docs/api/lookupCode) with `include=policies`, the codes of [`getPolicy`](/docs/api/getPolicy) with `include=codes`, and the policies in [`checkPriorAuth`](/docs/api/checkPriorAuth). The reference page of each endpoint that returns it links here.
* **FHIR output.** With `format=fhir`, each coverage item has an extension `https://backworkhealth.com/fhir/StructureDefinition/code-source` whose `valueCode` is the source. The item description of an inferred code says so.
* **Agent tools.** `check_coverage` marks a policy matched through an inferred code with `source: "inferred_title_match"` and adds a `known_gaps` entry. `find_policies` lists those codes in `inferred_codes`. See [Agent tools](/docs/agent-tools).
* **The Backwork app and public policy pages.** An inferred code has the label **Inferred from policy title**, with the explanation "Not listed in the policy document; attached because the policy title names the drug." A document-backed code has no label. Lists put document-backed codes first, and a list that contains inferred codes says what the label means above it.

## How to treat inferred codes [#how-to-treat-inferred-codes]

An inferred code is a lead, not a citation. Before you rely on one for a coverage, billing, or prior-auth decision:

1. Open the policy's `source_url` and confirm the document covers the drug and the code, for example through its dosing or billing section, or the payer's code list.
2. If you cannot confirm it, treat the policy as unconfirmed for that code and send the case to a person for review.
3. Do not present an inferred code to your users as listed in the policy. Label it the way the Backwork app does.

In code, branch on the field:

```typescript
const confirmed = policies.filter((policy) => policy.source === 'document');
const needsReview = policies.filter((policy) => policy.source === 'inferred_title_match');
```

The [sandbox](/docs/sandbox) has an inferred example: the code entries of `SBX03` have `source: "inferred_title_match"`.

## Grounding [#grounding]

Every code entry also has a `grounding`. It says whether Backwork found the code in the source text it kept for the policy.

| `grounding`      | Meaning                                                                                |
| ---------------- | -------------------------------------------------------------------------------------- |
| `grounded`       | The code is in the retained source text.                                               |
| `not_grounded`   | Backwork's document pipeline read the code, but it is not in the retained source text. |
| `no_source_text` | Backwork kept no source text to check.                                                 |
| `not_checked`    | Not checked. Every inferred code is `not_checked`.                                     |

Treat a `not_grounded` code like an inferred one: confirm it in the policy's `source_url` before you rely on it. The Backwork app and the public policy pages label it **Not found in the retained source text** and show nothing for the other values. With `format=fhir`, each coverage item has an extension `https://backworkhealth.com/fhir/StructureDefinition/code-grounding` whose `valueCode` is the grounding. `find_policies` lists these codes in `not_grounded_codes`.

For when Backwork fetched the policy itself and how accurate its source is, see [Source checks](/docs/source-checks).