Definition
InPOST /v3/verify responses, the identity object includes:
| Field | Role |
|---|---|
assuranceLevel | Tier such as AL-1, AL0, AL1, AL2, or AL3. Higher tiers indicate stronger confidence in the association between the phone number and the identity. |
reasons | One or more reason codes from the tables below (for example -1A, 1B). |
AL-1) to highest (AL3).
Reason codes
AL-1
| Reason code | Description |
|---|---|
| -1A | Too many identities bound to a single phone number. |
| -1F | Premium rate number globally or listed on the US Override Services Registry (OSR) registry. |
| -1G | Online rentable temporary eSIM or VoIP number. |
| -1H | Online rentable temporary eSIM or VoIP number, with high activity. This indicates fraudulent activity. |
AL0
| Reason code | Description |
|---|---|
| 0B | Country doesn’t give behavioral data. |
| 0C | Assigned number with no behavioral activity. |
| 0D | Short tenure, no activity. Reclassifies to AL0E if activity appears. |
| 0E | Short tenure with behavioral activity present. |
| 0F | Activity volume exceeds normal human thresholds. |
| 0G | Pagers or other non-standard line types. Behavioral signals incompatible with standard identity verification. |
AL1
| Reason code | Description |
|---|---|
| 1A | Enough ownership tenure and longitudinal human behavior. |
| 1B | Tenure and longitudinal human behavior with Prove binding phone to a specific identity, superseding AL1A. |
| 1D | Low longitudinal behavior but human signals such as ports, calls, or logins indicate not an eSIM bot. |
AL2
| Reason code | Description |
|---|---|
| 2A | Prove has seen this phone and identity before at moderate-to-high confidence. |
| 2B | Prove corroborated data across more than one identity data source. |
AL3
| Reason code | Description |
|---|---|
| 3A | Prove has seen this phone and identity before at high confidence, this is this person’s primary number. |

