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

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## 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.
For a virtual card transaction, Mastercard validates the controls on the virtual card first. If the transaction breaches the controls set, the transaction is rejected. If the virtual card controls are satisfied, Mastercard will check if there are any controls on the underlying real card. If the real card controls are breached, Mastercard will respond to the issuer with an advice to decline the real card transaction message to the issuer.

See [Example of card controls applied to both real card and virtual card](https://developer.mastercard.com/commercial-connect-api/documentation/use-cases/card-controls/index.md#example-of-card-controls-applied-to-both-real-card-and-virtual-card).

See [Card Controls: Elements and Attributes](https://developer.mastercard.com/commercial-connect-api/documentation/api-reference/card-controls/index.md) for more information.
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}