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Chapter 3 : A bit more Technical

Understanding Merchant Account Types, PDQ Terminal Connections & Compatibility

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IN THIS LESSON

When setting up your business to take card payments, one of the most important — and often overlooked — factors is making sure your merchant account and card machine (PDQ terminal) are compatible.

Choosing the wrong type of merchant account can result in your terminal not working at all. This is especially true with more complex connection methods like Daylink, Nightline, or bureau services, where specific technical links and IDs need to match behind the scenes.

In this guide, we explain the different merchant account types, terminal compatibility issues, TIDs (Terminal IDs), and what you need to consider before signing a contract.

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  • There are different types of merchant IDs (MIDs) depending on how you take payments. Each one is tailored to specific payment environments, so it’s vital to match the right MID to the correct terminal type.

    ✅ Common MID Types:

    • PSP (Payment Service Provider) MID

      • Used by all-in-one providers like SumUp, Zettle, Square

      • MID is shared or linked to an app-based account

      • Not compatible with traditional Daylink/Nightline terminals

      • Ideal for: Small businesses, quick-start setups, app-based readers

    • General MID / Direct MID

      • Set up with a bank or acquirer like Barclaycard, Worldpay, or Elavon

      • Supports traditional PDQ machines (Daylink/Nightline/Wi-Fi/SIM)

      • Suitable for in-store and MOTO payments

      • Ideal for: Established businesses, multi-terminal setups

    • Daylink MID

      • Requires a direct connection between terminal and acquiring bank

      • Must be matched with a Daylink-compatible terminal

      • Ideal for: Fixed-location businesses needing fast, secure payments

    • Nightline MID

      • Batch processes transactions overnight

      • Typically used with legacy terminals in older systems

      • Now largely replaced by real-time processing

      • Ideal for: Some legacy retail systems

    • Bureau MID

      • Transactions are processed via a third-party ‘bureau’ service on behalf of the merchant

      • Useful if you don’t have your own merchant account

      • Often used temporarily or for niche requirements

    • MOTO MID

      • For Mail Order / Telephone Order payments

      • Used with virtual terminals or over-the-phone systems

      • Not compatible with standard card-present PDQs

    🔔 Important: A Daylink terminal won’t work with a PSP MID, and vice versa. The technology and routing are different. Always make sure your terminal type and merchant account are matched correctly by the provider.

  • Every terminal connected to a merchant account is assigned a unique Terminal ID (TID). This allows the acquiring bank to:

    • Identify which terminal processed the payment

    • Link each transaction to the correct merchant account

    • Monitor performance and flag potential issues

    • Set different permissions for each device if needed

    📌 Key facts about TIDs:

    • A new TID is issued for each additional terminal

    • TIDs are assigned and uploaded during the terminal setup

    • TIDs must match the correct MID type (e.g. Daylink, MOTO, etc.)

    • Incorrect or missing TIDs will cause terminal errors or failed transactions

    🔧 Tip: If you’re upgrading or changing provider, always check your TIDs are correctly configured — especially if you're using multiple machines or locations.

  • Mismatched configurations can lead to:

    • Failed transactions

    • Terminal errors or "no comms" messages

    • Delayed settlements

    • PCI DSS compliance issues

    • Breach of contract terms

    • What type of merchant account is being provided?

    • Will it be a direct MID, a PSP account, or a bureau service?

    • Is the terminal compatible with the MID type?

    • Are your TIDs set up and correctly mapped?

    • Will you need multiple terminals, and do they each need a TID?

    • Are you using specialist features (like MOTO or eCommerce) that require different MIDs?

PDQ Terminal Connection Methods & Compatibility

Final Thoughts

Merchant accounts aren’t one-size-fits-all — and the technology behind them needs to be set up correctly from day one. A great rate means nothing if your terminal doesn’t work or fails during peak trading hours.

Always ask what type of MID you're being given, and make sure it’s compatible with the terminal, connection method, and payment flow your business needs.

🔍 Compare now or speak to an expert – no pressure, no jargon, just practical advice.