The Polished Geek AvaTax Connector plugin is free and open source (paid account with Avalara for AvaTax is required, however.)

Certified by Avalara for:
- Address validation (for all Avalara supported countries)
- Sales tax calculation, with geo-point accuracy
- Global sales tax - supports all international sales tax jurisdictions supported by Avalara
- VAT calculation, including physical and virtual goods
- Tax calculation support for partial or full refunds through HikaShop/HikaMarket
- Multi-vendor HikaMarket support delivers accurate tax calculation for multiple source addresses in a single order, by line item
- Compliant tax calculation in both the frontend and administrator backend, for accurate tax handling throughout the entire HikaShop or HikaMarket order lifecycle

Changelog:
v1.0.34 - Jan 2018 - bug fixes and improvements
v 1.0.22 - January 3, 2017 - Bug fix to send taxcode to Avalara for variants based on parent taxcode & added support for Joomla Updater.
v 1.0.26 - Bug fixes
v 1.0.28 - Improve coupon functionality to work with AvaTax line item allocation feature

AvaTax automation for your HikaShop or HikaMarket store makes taxes less taxing:

Fast

AvaTax applies US sales tax and VAT calculations as the transaction takes place via a secure, encrypted Internet connection without disrupting your existing workflow. Centralized, secure management enables tax schedules for new locations to be automatically assigned and maintained.

Easy

AvaTax integrates seamlessly with existing business systems and removes the guesswork. Rates are calculated “behind the scenes” and are automatically applied to the transaction. Reports are generated on-demand.

Accurate

Forget about tracking rates, rule changes and tax holidays. Forget about figuring out HikaShop tax zones, rates and rules. AvaTax continuously updates data, making accurate sales tax calculations available immediately. Minimize audit risk using advanced address validation, sourcing and taxability determination, and jurisdiction assignment technology.

With Avalara AvaTax seamlessly integrated in your HikaShop or HikaMarket store, your business is powered to handle even the most complex global tax situations and rules in the EU and beyond, including:
- U.S. companies selling to EU companies or consumers
- Intra-EU Transactions, including accurate tax calculation for virtual goods
- EU companies selling to companies or consumers in the U.S.
- EU companies with wholly owned subsidiaries in the U.S.