SumUp

Point of Sale ·6 min read ·Updated July 2026
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you take cards with a SumUp Solo and want the register to drive it, or you want to rehearse everything on the free Virtual Solo simulator first.

The POS sends the amount to a SumUp Solo card reader over SumUp’s Cloud API. SumUp is a favourite with small European merchants – cheap readers, no monthly contract – and the whole setup can be tested for free in a browser before a reader ever arrives.

Requirements

  • A SumUp account (SumUp operates in most of Europe plus the US, Brazil and Chile).
  • A SumUp Solo reader for live payments – the Cloud API drives the Solo. Older readers (Air, 3G, PIN+) work only with SumUp’s own app and cannot be used.
  • Three credentials, all from me.sumup.com → Settings → Developer: an API key, an Affiliate key and an Application ID.

Live and sandbox accounts – read this first

One SumUp login can own several merchant accounts: your real (live) one, and a sandbox account for testing. The Developer pages look identical for both – which account you are creating keys on is decided solely by the profile switcher in the top-left corner of the SumUp dashboard (the sandbox profile carries a yellow Sandbox badge).

The POS settings therefore include a Merchant account list showing every account your key can act for, with clear Live / Sandbox (test) badges. Readers, payments and refunds all run on the account you pick there – if a pairing ever fails with “Cannot pair virtual-solo with non-sandbox merchant account”, you are simply pointed at the wrong account in that list.

Get the credentials

  1. API key: Settings → Developer → API Keys → Create API key. The secret (sup_sk_…) is shown once in a popup – copy it immediately.
  2. Affiliate key + Application ID: Settings → Developer → Affiliate Keys. Add an application identifier (any name), then copy the affiliate key (sup_afk_…) and the identifier itself.
  3. In wp-admin go to POS → Card Terminals, set Active provider to SumUp, paste all three values and save.
  4. Under Merchant account, pick the account to charge (Live or Sandbox) and save again.

Pair a reader (live)

SumUp pairing runs in the opposite direction from other providers: the code is generated on the reader and typed into the website.

  1. On the Solo, log out if a user is signed in, then open the top menu → Connections → API → Connect. A pairing code appears (valid 5 minutes).
  2. In the POS settings click Pair a reader and enter the code.
  3. The Solo shows a confirmation, the reader appears in the list – pick it and save.

Sandbox setup (no hardware)

  1. Settings → Developer → Sandboxes → Create sandbox (one-time). Then switch the top-left profile to the sandbox account.
  2. Create the API key while on the sandbox profile and enter it in the POS settings; under Merchant account pick the one with the Sandbox (test) badge.
  3. Open Virtual Solo (virtual-solo.sumup.com – a button for it appears in the settings when a sandbox account is selected). It is a browser simulator of the Solo reader.
  4. On the Virtual Solo: Connections → API → Connect → pairing code → back in the POS settings click Pair a reader and enter it. The virtual reader appears in the list marked virtual-solo, test.

Sandbox behaviour: payments on the Virtual Solo auto-approve (no PIN), no real money moves, and an amount of exactly 11.00 always fails by design – use it to test the decline path.

Taking a payment

  1. Ring up the sale and choose Card – SumUp.
  2. The amount appears on the Solo; the register shows Waiting for card….
  3. The buyer taps or inserts. On approval the sale completes, the ticket is issued, and the SumUp transaction code is stored on the order.

Cancel stops the transaction on the reader (possible while it waits for the card or PIN). Note SumUp accepts one checkout per reader at a time – a second request within a minute of an unfinished one is rejected.

Refunds

Refund from the POS as usual – the card is refunded automatically through SumUp and the order gets a note: “Terminal refund sent to SumUp (card reversal).” Partial refunds are supported.

Troubleshooting

  • “Cannot pair virtual-solo with non-sandbox merchant account” – the selected Merchant account is the live one. Switch to the account with the Sandbox badge (and make sure the key was created on the sandbox profile).
  • Pairing code rejected – codes expire after 5 minutes; generate a fresh one on the reader.
  • Checkout not accepted – the Solo must be online (it prefers Wi-Fi); keep it plugged in when driven via the Cloud API.
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