# Support
source: https://developer.mastercard.com/commercial-connect-api/documentation/support/index.md

## FAQ {#faq}

### General {#general}

A Virtual Card Number (VCN) is a credit card number, which is generated dynamically for a particular payment purpose. It is created with a limited validity period and [controls](https://developer.mastercard.com/commercial-connect-api/documentation/api-reference/card-controls/index.md) on how it should be spent. Corporate buyers can create virtual cards to pay supplier invoices and cover business expenses.

For more information about VCN use cases, see [Virtual Cards](https://developer.mastercard.com/commercial-connect-api/documentation/use-cases/vcn/index.md).

For more information about card controls, see [Card Controls: Elements and Attributes](https://developer.mastercard.com/commercial-connect-api/documentation/api-reference/card-controls/index.md) and [Card Controls Use Cases](https://developer.mastercard.com/commercial-connect-api/documentation/use-cases/card-controls/index.md).

### Card controls {#card-controls}

Available balance is an element of both `agingLimit` and period limit controls. The system calculates the available balance based on the `spendAmount` limit and the duration of the limit that you have specified, and the amount spent. For more information and use cases involving available balance, see [Available balance](https://developer.mastercard.com/commercial-connect-api/documentation/use-cases/card-controls/index.md#available-balance). This aging limit tracks the current remaining available credit and approves a transaction only if the requested amount is less than or equal to the remaining available credit. See [How to use aging limit and period limit controls](https://developer.mastercard.com/commercial-connect-api/documentation/use-cases/card-controls/index.md#how-to-use-the-aging-limit-and-period-limit-controls) to learn how to use the aging limit. See [Card Controls: Elements and Attributes](https://developer.mastercard.com/commercial-connect-api/documentation/api-reference/card-controls/index.md) for more information about the aging limit definition. Commercial Connect API provides real-world examples in the context of [card controls](https://developer.mastercard.com/commercial-connect-api/documentation/api-reference/card-controls/index.md), such as using the aging limit spend amount. These examples help clients understand how to set up card controls for their various needs, for example setting a budget for business cards. For more real-world-examples and card control information, see:

* [Example of when to use the aging limit spend amount](https://developer.mastercard.com/commercial-connect-api/documentation/use-cases/card-controls/index.md#example-of-when-to-use-the-aging-limit-spend-amount).
* [Example of when to use the aging limit with other controls](https://developer.mastercard.com/commercial-connect-api/documentation/use-cases/card-controls/index.md#example-of-when-to-use-the-aging-limit-with-other-controls).
* [Card controls](https://developer.mastercard.com/commercial-connect-api/documentation/api-reference/card-controls/index.md).

### Onboarding {#onboarding}

To get started with Commercial Connect API and learn about how to create a project for the service, authentication, credentials, Sandbox and Production access, see the [Quick Start Guide](https://developer.mastercard.com/commercial-connect-api/documentation/quick-start-guide/index.md).

For more information about SLAs, see the [Onboarding Checklist](https://developer.mastercard.com/commercial-connect-api/documentation/onboarding-checklist/index.md).

### Policy {#policy}

The throttling policy for Commercial Connect API is as follows: 500 requests per second. Yes, all of Commercial Connect APIs are payment card industry compliant.

### Performance {#performance}

The Throughput per Second (TPS) per customer is 1.00 KB/s. The average response time is 3 seconds.

### Support {#support}

Contact a Mastercard representative through [commercial.support@mastercard.com](mailto:commercial.support@mastercard.com).

## Get Help {#get-help}

### Contact us for technical support. {#contact-us-for-technical-support}