# Understand offline tax calculation

Source: https://developer.avalara.com/products/communications/integration-guides/communications-integration/fpj6356196612116/

Guide: Communications

# Understand offline tax calculation

Learn how to handle connection issues and ensure that tax calculations continue during outages.

Designing robust software means to plan 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, you can write your software to handle an outage smoothly.

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’re 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’s 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 page:

-   Subscribe to Updates for the services that 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