21Bill is an invitation-only, browser-based billing and GST compliance platform for Indian SMBs. It simplifies invoicing, vendor bill tracking, and GSTR-1/3B filing with one-click JSON exports. The AI assistant provides plain-English GST summaries, and the API-first design enables seamless integration. Trusted by 20 lakh+ businesses, it's faster than Tally and simpler than Vyapar.