# Chapter 6 - Calculating Tax Offline

Source: https://developer.avalara.com/products/communications/integration-guides/dev-guide_rest_v2/calculating-tax-offline/

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Designing robust software means planning for every eventuality. To create a world-class product using Communications REST v2, you need to be prepared for when things go wrong - and one of the problems you may face is an outage. Fortunately, there are ways to write your software to gracefully handle an outage.  

Types of connection issues:

-   Temporary Outage: Your connection has gone offline and you need to be able to process transactions for a short period of time until the connection is restored
-   Intermittent Connection: Your connection works most of the time, but its behavior is unpredictable and occasionally drops unexpectedly
-   Unable to Reach REST v2: Your connection is up, but you are unable to reach REST v2 because of a routing problem, a denial-of-service attack on an Internet service provider, or a temporary outage of REST v2

These types of outages have similar characteristics, so it’s straightforward to design a single process to handle all of them. Here is how we handle a broken connection:

-   Detect the dropped connection and prevent a crash
-   Retry the transaction
-   Recover data using the Commit/Uncommit functionality
-   Reconcile transactions after the outage

As a cloud-based Software-as-a-Service provider, Avalara understands the need to ensure that our services are available continuously and respond in a timely manner. Check out the [Avalara Server Status](https://status.avalara.com) page:

-   **Subscribe to Updates** for the services you use - see **Avalara Communications** for REST v2 status
-   Shows the current availability of all Avalara services
-   Displays graphs detailing current response times for a number of Avalara services
-   Provides a historical view of availability

-   [Previous Chapter](/communications/dev-guide_rest_v2/reference)
-   [Next](/communications/dev-guide_rest_v2/calculating-tax-offline/detect-dropped-connection/)