What’s a Merchant ID Number? (and How to Get One)

A merchant identification number (MID) is a unique code that helps identify a merchant account. It is generated by the payment processor after the account has been created and is used to complete different actions at various stages throughout the payment processing lifecycle.

Like a phone number that routes calls to your individual phone or an email address that directs messages to your personal inbox, a MID ensures funds are deposited into your account and no one else’s. It also prevents you from receiving refunds and chargebacks that don’t belong to you. 

Want to know more about MIDs? Check out these seven frequently asked questions and our detailed responses.

• Why do merchants need a MID?
• How do merchants get a MID?
• How can merchants find their merchant ID number?
• What other payment processing IDs are there? 
• Can merchants have multiple MIDs?
• Can merchants lose their MID?
• How can merchants protect their MID?

Your MID is used for a variety of different things, and you’ll probably need to enter it in a couple different platforms such as your CRM or order management system, your gateway, your fraud filter, and your chargeback management technology. 

Since MIDs are usually long strings of numbers and/or letters, they are hard to memorize. You’ll probably need to look yours up when it comes time to use it. 

There are a couple different places you can find your merchant ID:

• When the processor approved your merchant account application, you probably received a VAR (value-added reseller) sheet. Along with other account details, the VAR sheet shares your MID. (A VAR sheet is sometimes referred to as a tear sheet or parameter sheet.)
• A merchant account agreement typically lists the MID.  
• Your MID is printed on your monthly merchant statement, which is like a bank statement for your account.
• If your processor has an online account portal, your MID is probably included with other account information. 

• Terminal ID – This unique code helps you identify the point-of-sale (POS) terminal used to process the transaction. 
• Gateway ID – Also referred to as a CRM account ID, this is a unique name or number assigned by the CRM or order management system to identify the merchant account used to process the payment. 
• Order ID – Your CRM or order management system assigns a unique identifier to each order you process. 
• CRM ID – An identifier can help you determine which CRM was used to process the payment (if you have more than one CRM or order management system).
• ARN – Your acquirer assigns a unique identifier, called the acquirer reference number, to each transaction. 
• BIN – Bank identification numbers are used to identify financial institutions. Both issuing banks and acquiring banks have them (BINs from a card issuer are the first six digits on the payment cards issued by that bank). 
• MCC – Your merchant category code identifies the type of goods or services you sell.

Some merchants only need one MID; other merchants require multiple merchant IDs.

Merchant accounts have restrictions on the types of transactions that can and can’t be processed (for example, ecommerce or in-person, but not both). They also have limits on transaction and sale volumes (for example, a maximum of $250,000 a month). 

That means that if your business grows and evolves over time, it may need different MIDs to handle the different debit and credit card processing situations.

For example, making any of the following changes to your business could mean you need to add more MIDs:

• Your sales volume increases significantly
• You expand your business model (open an ecommerce store, add a restaurant to your t-shirt shop, etc.)
• You switch from domestic to international sales

It is possible to lose your MID. 

However, you technically don’t lose your merchant ID; what you lose is your ability to process payments. If your processor decides to revoke your processing privileges, your merchant account will be closed and its identification number will eventually cease to exist. 

There are several reasons why you might lose your ability to process debit or credit card payments. For example, your account will be terminated if your processor discovers you are laundering money or selling prohibited items. 

But the most common reason for merchant account closures is chargebacks. 

The card brands have set risk thresholds and carefully monitor chargeback activity. If your chargeback counts become excessive and you breach the thresholds for high risk — or your processor suspects you might — your processing privileges can be revoked.