A payment device is provided, which is to be paired with a communication device in order to form an electronic payment terminal. The payment device includes an upper half-shell and a lower half-shell, which includes a surface for attaching a modular interface for pairing the communication device and which includes a longitudinally extending slot. The lower half-shell further includes, within the slot, an opening which enables a magnetic reading head to pass therethrough. Beneath the attachment surface, an electronic circuit card is arranged laterally relative to the magnetic reading head such that the electronic circuit card prevents the insertion of a fraudulent device into the payment device.