> ## Documentation Index
> Fetch the complete documentation index at: https://help.mathership.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Linking Existing Customers

> Connect an existing Mathership customer company to your vendor account

# Linking Existing Customers

Vendors can link an existing customer company to their vendor account.

Use this when the restaurant or customer already has a Mathership account and should be connected to your vendor company without creating a duplicate customer.

## What does linking an existing customer mean?

Linking an existing customer creates a vendor-customer relationship between your vendor company and an already existing customer company.

After the relationship is created, the customer can use your vendor company in Mathership, depending on their access and available features.

## When to link an existing customer

Link an existing customer when:

* The customer already has a Mathership account
* The customer company already exists in Mathership
* You want to connect the customer to your vendor company
* You do not want to create a duplicate customer
* You want to assign your own customer number to that customer

## How linking works

When you link an existing customer, Mathership uses the existing customer company and creates a new relationship to your vendor company.

The customer company itself is not recreated.

| Item                         | Result               |
| ---------------------------- | -------------------- |
| Existing customer company    | Reused               |
| New customer user            | Not created          |
| Vendor-customer relationship | Created              |
| Customer number              | Optional             |
| Email notification           | Sent to the customer |

## Required information

To link an existing customer, Mathership needs the existing customer company.

| Field           | Required | Description                                     |
| --------------- | -------- | ----------------------------------------------- |
| Customer        | Yes      | Existing customer company                       |
| Customer number | Optional | Your internal customer number for this customer |

<Note>
  Customer numbers are stored on the relationship between your vendor company and the customer company.
</Note>

## Link an existing customer

To link an existing customer:

1. Go to **Vendor**
2. Open **Customers**
3. Select **Add Customer** or **Link Existing Customer**
4. Search for the existing customer
5. Select the matching customer company
6. Add a customer number, if needed
7. Confirm the connection

After confirming, Mathership creates the customer relationship.

## What happens after linking?

After the customer is linked:

* The customer appears in your customer list
* The customer relationship is active
* The customer number is saved, if provided
* The customer receives an email notification
* The customer can be used in related vendor workflows

## Duplicate protection

Mathership prevents linking the same customer twice.

If the customer is already added to your vendor account, the connection is not created again.

<Warning>
  Do not create a new customer if the customer already exists. Link the existing customer instead to avoid duplicate records.
</Warning>

## Customer numbers

You can assign a customer number while linking the customer.

Example:

| Field           | Example         |
| --------------- | --------------- |
| Customer        | Main Restaurant |
| Customer number | 4711            |

Customer numbers are useful when you also manage customers in another system, such as an ERP, accounting system, or delivery system.

## Existing customer not found

If the customer cannot be found, check:

* The customer email address
* The company name
* Whether the customer already has a Mathership account
* Whether the customer was created with a different email address

If the customer does not exist yet, create a new customer instead.

## Common problems

### Customer is already added

This means a relationship between your vendor company and this customer already exists.

You do not need to link the customer again.

### Customer number already exists

This means the customer number is already used in your vendor account.

Use another customer number or check whether the customer is already linked.

### Selected company is not a customer

Only customer companies can be linked as customers.

Vendor accounts cannot be linked as customers.

### Customer did not receive the email

Ask the customer to check:

* Spam folder
* Correct email inbox
* Mail filters
* Whether another person in the company received the message

## Related pages

<CardGroup cols={2}>
  <Card title="Add Customer" icon="user-plus" href="/en/vendors/customers/add-customer">
    Create a new customer company.
  </Card>

  <Card title="Invite Customers" icon="envelope" href="/en/vendors/customers/invite-customers">
    Invite customers to connect with your vendor account.
  </Card>

  <Card title="Customer Details" icon="address-card" href="/en/vendors/customers/customer-details">
    View customer information and delivery locations.
  </Card>

  <Card title="Customer Numbers" icon="hashtag" href="/en/vendors/customers/customer-numbers">
    Manage customer numbers for linked customers.
  </Card>
</CardGroup>