---
title: "Fixing participant registration errors"
description: "How to fix the most common errors when registering participants in Signer: EmailAlreadyBeingUsed, CpfAlreadyBeingUsed, DuplicateUser, a signature with someone else's name and the same e-mail for different people."
canonical: "https://docs.lacunasoftware.com/en-us/articles/signer/user-guide/erros-de-cadastro"
locale: "en"
product: "Signer"
last_updated: "2026-10-22"
---

# Fixing participant registration errors

This page lists the most common errors when Signer links a participant to a user. For each error, it gives the
cause and the fix. To understand how Signer searches for the user, see
[Participant identification](https://docs.lacunasoftware.com/en-us/articles/signer/concepts/participant-identification).

## `EmailAlreadyBeingUsed`

Signer tried to create a new user, but the e-mail already belongs to another GrantID account. This happens, for
example, when the participant has a new CPF and an e-mail that already exists.

Use the e-mail of the existing account or a new e-mail. If one mailbox must serve more than one person, see
[Same e-mail for people with different CPFs](https://docs.lacunasoftware.com/en-us/articles/signer/user-guide/erros-de-cadastro#shared-email).

## `CpfAlreadyBeingUsed`

The same applies to `PassportAlreadyBeingUsed`, `RucAlreadyBeingUsed` and the other errors of this kind. The
identifier already belongs to another account, and its mode is unique.

Check that the identifier is correct. If the person already has an account, use that account's e-mail.

## The signature comes out with someone else's name or CPF

Signer searched by e-mail and found another user. See the
[example](https://docs.lacunasoftware.com/en-us/articles/signer/concepts/participant-identification#matching).

Use one e-mail per person, or switch the instance to search by CPF. See
[Same e-mail for people with different CPFs](https://docs.lacunasoftware.com/en-us/articles/signer/user-guide/erros-de-cadastro#shared-email).

## Same e-mail for people with different CPFs

A holder and a dependent are one example. By default, the e-mail is unique in GrantID.

Ask support for this combination: GrantID sign-in by CPF, CPF in `Unique` mode, non-unique e-mail in GrantID, and
`EnableMultipleIdentifiersPerUser` off. It only works with all four.

## `DuplicateUser`

The request has the same user more than once.

Remove the repeated participant.