> For the complete documentation index, see [llms.txt](https://docs.verifone.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.verifone.com/api-reference/open-api-references/checkout/error-codes.md).

# Error Codes

Every Checkout API error response returns a JSON object with the following fields:

<table><thead><tr><th width="142.3333740234375">Field</th><th width="149.77783203125">Type</th><th>Description</th></tr></thead><tbody><tr><td><code>code</code></td><td>number</td><td>3-digit Verifone error code</td></tr><tr><td><code>timestamp</code></td><td>string</td><td>ISO 8601 timestamp of the error</td></tr><tr><td><code>message</code></td><td>string</td><td>Human-readable description</td></tr><tr><td><code>details</code></td><td>object</td><td>Optional additional context</td></tr></tbody></table>

{% hint style="info" %}
When debugging a `400` error, always check the `details` field — it will identify which specific request parameter is invalid or missing.
{% endhint %}

## Common Error Codes

{% tabs %}
{% tab title="400 Bad Request" %}

<table><thead><tr><th width="178">Verifone Code</th><th>Cause</th></tr></thead><tbody><tr><td><code>107</code></td><td>Invalid parameter format — check <code>details</code> for affected fields</td></tr><tr><td><code>110</code></td><td>Invalid resource or malformed JSON</td></tr><tr><td><code>126</code></td><td>Missing required parameter</td></tr><tr><td><code>123</code></td><td>Transaction rejected by processor</td></tr><tr><td><code>127</code></td><td>Unexpected parameter submitted</td></tr></tbody></table>
{% endtab %}

{% tab title="401 / 403" %}

<table><thead><tr><th width="93.111083984375">HTTP</th><th width="122">Verifone Code</th><th>Cause</th></tr></thead><tbody><tr><td>401</td><td><code>116</code></td><td>Authentication required — check <code>Authorization</code> header</td></tr><tr><td>403</td><td><code>111</code></td><td>Transaction blocked by organisation ruleset</td></tr><tr><td>403</td><td><code>113</code></td><td>Insufficient permissions for this operation</td></tr><tr><td>403</td><td><code>121</code></td><td>Transaction declined by processor</td></tr><tr><td>403</td><td><code>165</code></td><td>Checkout exceeded maximum failed transaction attempts (3)</td></tr><tr><td>403</td><td><code>168</code></td><td>Checkout already completed</td></tr><tr><td>403</td><td><code>169</code></td><td>Checkout has expired (max 30 days)</td></tr></tbody></table>
{% endtab %}

{% tab title="404 / 500 / 504" %}

<table><thead><tr><th width="105.3333740234375">HTTP</th><th width="126">Verifone Code</th><th>Cause</th></tr></thead><tbody><tr><td>404</td><td><code>109</code></td><td>Resource not found</td></tr><tr><td>500</td><td><code>100</code></td><td>Unexpected server error — contact support with <code>code</code> and <code>timestamp</code></td></tr><tr><td>504</td><td><code>170</code></td><td>API call timed out — retry the request</td></tr></tbody></table>
{% endtab %}
{% endtabs %}

## Checkout-Specific Codes

These codes are unique to the Checkout API lifecycle:

{% columns %}
{% column %}

#### Session State Errors

* **`165`** — The session has exceeded 3 failed payment attempts. Create a new checkout session.
* **`168`** — The session has already been completed. No further payments can be made.
* **`169`** — The session has expired (sessions are valid for up to 30 days). Create a new checkout session.
  {% endcolumn %}

{% column %}

#### Recommended Actions

* For `165` / `168` / `169`: always create a fresh checkout via `POST /v2/checkout`
* For `100` server errors: log the full `code` and `timestamp` and contact Verifone support
* For `170` timeouts: implement an exponential back-off retry strategy
  {% endcolumn %}
  {% endcolumns %}


---

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