Medius Extends Tax Verification in AP Automation with Avalara AvaTax Integration

Integration allows businesses to verify US sales and use tax against Avalara AvaTax before invoices are posted to the ERP

Medius, a leading provider of accounts payable automation and spend management solutions, today announced an integration between Avalara AvaTax indirect tax determination and Medius AP Automation, enabling businesses to verify US sales and use tax on every invoice, within the approval workflow and before it posts to the ERP.

As invoices move through the Medius workflow, vendor-charged US sales and use tax is recalculated against Avalara's determination service, with overcharges and undercharges automatically flagged before payment. Customers already running Avalara AvaTax can apply the same tax logic inside the AP approval process they use every day, without a separate platform or a new manual review step. 

For finance teams operating across thousands of US tax jurisdictions, ensuring the correct tax is applied to every invoice can be challenging. Incorrect vendor-charged tax can lead to businesses paying tax they do not owe, while missed use-tax obligations can create unexpected liabilities and increase audit exposure. With the integration, each invoice is verified line by line and jurisdiction by jurisdiction as it moves through Medius AP Automation. 

"Most of our customers settled the question of which tax engine to run years ago," commented Gary Hall, Chief Product Officer, Medius. "What they haven't solved is timing. The determination is accurate, but it arrives after the invoice has been approved and paid, which turns every correction into a recovery exercise. We moved the check upstream, into the approval step. It is a small change in sequence and a large change in what it costs to get tax wrong."  

A rapidly expanding financial compliance ecosystem 

The Avalara AvaTax integration is the latest example of Medius’ financial compliance extensibility, following the Thomson Reuters ONESOURCE integration announced earlier this month. Medius is committed to developing connectivity to the critical systems that customers know and trust directly into their existing AP workflow, allowing finance teams to maintain their infrastructure without taking on a separate integration project. 

“As tax rules continue to shift across thousands of jurisdictions, our goal is to deliver accurate determination at the exact moment financial decisions are made,” said Greg Chapman, General Manager of AvaTax at Avalara. “By embedding AvaTax directly into the Medius approval workflow, invoices are verified before they post, ensuring greater accuracy upfront rather than catching costly errors after payment has already gone out.” 

Medius and Avalara share 250+ mutual customers today. For those businesses, the integration introduces no new platform and no change to how tax is determined, only to when verification happens in the invoice lifecycle. The approach is focused on customer optionality; businesses can adopt Medius without changing tax engines and continue using Avalara without limiting their choice of AP automation platform. 

Medius offers an open set of APIs and dedicated development resources for third-party extensibility, with additional integrations across tax, compliance and other key financial systems to follow. 

The Medius team will be exhibiting at Avalara CRUSH 2026 in Fort Lauderdale through September 24. The team is meeting with finance, tax and IT leaders to demonstrate how tax verification works within the AP approval workflow, including exception handling and activation for existing Avalara deployments.

Contact 

For more information, please contact: Emma Silva at Fight or Flight, emma.silva@fightorflight.com / Medius@fightorflight.com 

About Medius 

Medius links invoice capture, processing, and payment to replace the worry and wondering of managing AP with calm and confidence. Medius goes far beyond basic automation by using artificial intelligence to do most of the work – so invoices get confirmed, coded and paid; AP teams get to go home and rest easy; and businesses can trust their budgets and forecasts. Medius, on a mission to transform the spend management category using the power of automation and AI, has more than 4,000 customers across 116 countries and processes $300 billion in annual spend through its system. Visit medius.com to learn more. 

About Avalara 

Avalara is the agentic AI leader in global tax and compliance. For more than two decades, Avalara’s trusted tax content, deep compliance expertise, proprietary data, and technology have helped customers succeed on a global scale. Avalara now pairs that foundation with agentic AI to help businesses execute complex compliance work while keeping people in control. Avalara processes more than 54 billion AvaTax API calls annually and supports millions of businesses worldwide. For more information, visit Avalara.com.  

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