# XBC-001 — Sole proprietor brands may only run the sole proprietor use case

> A SOLE_PROPRIETOR brand must register its campaign under the SOLE_PROPRIETOR use case; standard campaign types are unavailable to that tier.

- **Rule ID:** XBC-001
- **Layer:** Brand ↔ campaign (`CROSS`)
- **Checks:** `brand.entity_type + campaign.usecase`
- **Severity:** BLOCKING — Breaking this rule gets the submission rejected outright.
- **When it bites:** Gates approval — get this wrong and registration is refused
- **How it is detected:** Deterministic (settled in code from the submitted values)
- **Fix type:** Fix the field — a better value in the form clears it
- **Required by:** TCR, Twilio
- **Applies:** Applies when the brand is a sole proprietor.
- **Depends on:** BRD-065
- **Canonical URL:** https://ekas.io/rules/10dlc/cross/xbc-001/

## Why this rule exists

The sole proprietor tier exists as a low-volume path for individuals with no EIN, and it comes with its own throughput caps and a single-number limit. Standard use cases assume a vetted registered entity behind them, so the platform refuses the combination rather than granting an individual standard-tier treatment.

## How to fix it

Select the Sole Proprietor use case for this campaign. If you need a standard use case such as Marketing, obtain an EIN and re-register the brand as a standard entity first — the tier, not the campaign, is what limits you.

## Example of a compliant value

```text
Use case: SOLE_PROPRIETOR
```

## Notes

Catalog BRD-089. The most common failure after a sole proprietor brand is itself accepted.