neo.tax - automated R&D tax credits for startups = extra month of burn
Quarterly Tax Calculator Bot - Quarterly tax calculation for freelancers
Stripe Atlas Taxes - Help file your business taxes
Taxfyle - Stop doing your taxes, leave it to the professionals.
TaxDrop - Get your taxes done in 10 minutes
DocSpring - DocSpring provides a PDF filling API that makes it easy for programmers to fill out and generate PDF documents.