> For the complete documentation index, see [llms.txt](https://docs.payments.thalescloud.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.payments.thalescloud.io/nfc-wallet-sdk-android/implement-nfc-wallet/make-payment/implement-contactless-payments.md).
# Implement contactless payments
## Overview
The NFC Wallet SDK supports multiple contactless payment payment experience on Android:
* **Single-tap**: Only one tap is required to handle the transaction with point-of-sale (POS) terminal with or without end user authentication.
* **Two-tap** End users needs 2 taps with POS to handle transaction, the first tap to open the digital wallet application to required end user authentication.
* **Manual mode**: The end user opens your digital wallet application and starts a payment from the in-app UI.
Choose the experience that matches your digital wallet application UX.
### Android settings
Android settings can affect the payment experience. Check these settings before you start:
* Check that your digital wallet application is the default payment application. This is required for **single-tap** and **two-tap** payments.
See [Default payment application](/nfc-wallet-sdk-android/help/knowledge-base/control-nfc-payments-on-android.md#default-payment-application).
* Check whether Android allows the foreground application to override the default payment application. This can affect **manual mode** payment experience.
See [Pay with foreground app](/nfc-wallet-sdk-android/help/knowledge-base/control-nfc-payments-on-android.md#pay-with-foreground-app).
## User experience
### Single-tap
With **single-tap** experience end user brings the device close to a POS terminal only one time to perform the contacless transaction with or without a pre-authentication.
#### **With authentication**
In this experience end user needs to unlock the device using a CDCVM method (**biometric** or **keyguard**) before the tap.
{% hint style="warning" %}
The tap must be performed within a configured validity period after authentication to unlock device.
See `keyValidityPeriod` in [Configure payment behavior](/nfc-wallet-sdk-android/get-started/configuration/4.-initialize-the-nfc-wallet-sdk.md#configure-payment-behavior).
{% endhint %}
{% hint style="info" %}
See [Activate pre-entry](/nfc-wallet-sdk-android/implement-nfc-wallet/make-payment/implement-contactless-payments/3.-consider-application-start.md#activate-pre-entry) to support this payment experience.
{% endhint %}
#### Without authentication
End users doesn't need to authenticate to perform the single-tap transaction in the following case:
* **Low value transaction (LVT)**
Transaction below a amount and for a dedicated currency.
* **Transit transaction**
Transaction without authentication to allow a frictionless payment experience at transit gate.
See [Configure CDCVM experiences](/nfc-wallet-sdk-android/implement-nfc-wallet/make-payment/implement-contactless-payments/7.-configure-cdcvm-experiences.md) for more details.
### Two-tap
With **two-tap** experience end user brings the device close to a POS terminal, the OS launches the default digital wallet application to request end user authentication. Once authenticated the end-user could be perform the transaction by executing the 2nd tap.
{% hint style="warning" %}
The 2nd tap must be performed within a configured validity period after authentication.
See `keyValidityPeriod` in [Configure payment behavior](/nfc-wallet-sdk-android/get-started/configuration/4.-initialize-the-nfc-wallet-sdk.md#configure-payment-behavior).
{% endhint %}
{% hint style="info" %}
As an option end user could select the card to pay before the 2nd tap.
{% endhint %}
### Manual mode
In this experience, the end user starts the payment from within your digital wallet application. You implement the UI and the action that triggers the payment flow.
## Implementation guides
After you choose the contactless payment experience for your digital wallet application, implement contactless payment in this order:
1. [Implement HCE service](/nfc-wallet-sdk-android/implement-nfc-wallet/make-payment/implement-contactless-payments/1.-implement-hce-service.md)\
Implement the Android HCE service used for contactless payments.
2. [Implement contactless payment callbacks](/nfc-wallet-sdk-android/implement-nfc-wallet/make-payment/implement-contactless-payments/2.-implement-contactless-payment-callbacks.md)\
Handle NFC Wallet SDK callbacks during a contactless payment.
3. [Consider application start](/nfc-wallet-sdk-android/implement-nfc-wallet/make-payment/implement-contactless-payments/3.-consider-application-start.md)\
Ensure your digital wallet application is ready when a payment starts.
4. [Support manual mode](/nfc-wallet-sdk-android/implement-nfc-wallet/make-payment/implement-contactless-payments/4.-support-manual-mode.md)\
Add app-side support for manual mode payments.
5. [Perform CDCVM verification](/nfc-wallet-sdk-android/implement-nfc-wallet/make-payment/implement-contactless-payments/5.-perform-cdcvm-verification.md)\
Verify **CDCVM** and handle fallback when required.
6. [Display transaction context](/nfc-wallet-sdk-android/implement-nfc-wallet/make-payment/implement-contactless-payments/6.-display-transaction-context.md)\
Show transaction details to the end user.
7. [Configure CDCVM experiences](/nfc-wallet-sdk-android/implement-nfc-wallet/make-payment/implement-contactless-payments/7.-configure-cdcvm-experiences.md)\
Enable **single-tap** without authentication for LVT and/or transit transaction.
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