> ## Documentation Index
> Fetch the complete documentation index at: https://voucherify-pw-further-tests.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Add Referral Code Holders

> Adds new holders to a referral code as **referees**. The data sent in the request is upserted into the customer data.

If the request returns an error even for one customer, you have to resend the whole request. Customer data is upserted if the data for all customers is correct.

To use this endpoint, you must have the following permissions:
- Create and modify Customers and Segments (`customers.modify`)
- Publish Voucher (`vouchers.publish`)

> 👍
>To add a holder as a referer, use the [Create Publication](ref:create-publication) endpoint.