DIY Tax Return, Cogno AI's AI-powered Self Assessment platform, is now live in production at diytaxreturn.co.uk. UK taxpayers can prepare and file their Self Assessment with AI help. We did not get there alone. Our technology partner Workstation worked with us from inception to launch. They provided the AI agents and edge infrastructure that took the product from its first commit to production.
From Inception to Launch with Workstation
Workstation built the delivery platform behind DIY Tax Return: Kubernetes environments, CI/CD pipelines, observability and the edge gateway. Their AI agents worked alongside our engineers at every stage. That meant a small team could build, test and harden an HMRC-connected product at a fraction of the usual cost and time.
AI Agents Across the Lifecycle
Development agents: AI coding agents built and refactored the FastAPI backend, the Next.js web app, the iOS app and the HMRC Making Tax Digital integration, with an engineer reviewing every change. Every pull request also went through an AI reviewer before merge.
QA agents: More than 18 automated end-to-end suites run the real tax journey on every change and every night. They cover registration, bank statement upload, AI extraction, transaction classification, reconciliation, tax calculation and HMRC filing. When a build fails, an AI build-fixer agent diagnoses it and proposes a fix.
Deployment agents: Releases move through five isolated rings (dev, int, test, acc and prod), and a ring promoter only moves a build forward when the ring before it is green. Every environment is declared in Helm and GitOps, so production is a reproducible copy of what was tested.
WSL WAF, API Gateway and Edge Gateway
All traffic to DIY Tax Return, in every environment, passes through Workstation's WSL edge gateway:
- Web Application Firewall filtering malicious traffic before it reaches the application
- API gateway routing with weighted backends per environment, keeping int, test, acc and prod isolated
- TLS termination and edge caching for fast, secure delivery
- Declarative gateway rules in version control, checked in CI and scanned for drift automatically
Built Against HMRC MTD Requirements at Every Stage
Software that files Self Assessment through HMRC's Making Tax Digital APIs has to meet HMRC's technical and fraud-prevention requirements. Those checks run automatically in the pipeline:
- Gov-Client and Gov-Vendor fraud-prevention headers for web and iOS, tested against HMRC's official validator on every change and on a weekly schedule
- The full filing journey tested end to end against HMRC's sandbox before a build can be promoted
- OAuth 2.0 connection to HMRC, with the user's National Insurance number checked before connecting
- Users review their figures before anything is sent to HMRC, and every submission is audit-logged
- Automated backups and disaster-recovery restore drills
Built for Thousands of Users, at Low Cost
DIY Tax Return is built to handle thousands of UK taxpayers filing their Self Assessment with AI, including the January deadline rush. Using AI agents for development, QA and operations, and generative AI in the product itself, kept costs down in several ways. The team stays small, infrastructure costs less per user, and every generative AI call is traced so model costs and quality stay under control.
Those savings go to users as one of the most affordable ways to file a UK tax return. Read the launch story on the DIY Tax Return blog, or learn more about our technology partner at workstation.co.uk.