Thomson Reuters ONESOURCE - ONESOURCE tax software and solutions synchronize every aspect of your work and link international, country, state and local tax laws.
TaxJar - TaxJar simplifies sales tax filing for eCommerce sellers.
Avalara - Cut tax compliance costs, not corners. Avalara automates tax compliance and can help improve accuracy while reducing costs.
vatlayer API - Free VAT Validation & EU VAT Rates API
VatStack - Simplify VAT & GST for your digital business.
Quaderno.io - Quaderno for Stripe is the simplest way to bill your customers without programming a single line of code.