# `missing_value`: a comparison was withheld because a value was missing

Both signals answered, but one of the two fields the comparison needs was null, so nothing was compared.

- Appears in: `flag`
- Billing: Free. The consistency analysis is arithmetic over answers already paid for and never costs a credit of its own.

A null field means not evaluated, never no. An invalid phone number carries no country, a reserved IP carries no location, and an address outside every installed register carries no mail-drop answer.

The comparison is reported with result `not_compared` so you can see it was considered rather than silently dropped.

**What to do.** Nothing to act on. Supply the missing signal, or read the per-signal block to see why the field was null.

```json
{
    "comparison": "ip_phone_country",
    "left": {
        "signal": "ip",
        "field": "country",
        "value": "GB"
    },
    "right": {
        "signal": "phone",
        "field": "country",
        "value": null
    },
    "result": "not_compared",
    "withheld": "missing_value",
    "flag": null
}
```

Reference: https://spaw.co/docs/reasons/missing_value