Use Claude to fill HMRC forms from local calculations

Giuseppe Santoro had already used Claude Code to write Python calculations for income and capital gains. The remaining difficulty was working through HMRC's questions and entering values. His records covered stocks, mentoring, newsletter revenue and savings interest.

He connected Playwright MCP to Claude Code so the agent could navigate the browser while retaining access to local files. Earlier browser approaches lacked access to his calculations and supporting data, leaving him to copy information between environments. With the bridge in place, he asked Claude to open the HMRC form, read its questions and fill answers from local income data.

Santoro describes completing the form work in a few hours spread across several days. He remained involved through conversation, including spoken questions about what individual fields meant and whether they applied to his situation. The published prompt excerpt records that explanation step, rather than a complete instruction to submit a return.

He converted what he learned into a reusable Claude Code skill for the next financial year. The demonstrated result is browser form filling with local context and interactive explanations. The article does not describe a separate unattended submission or payment checkpoint.

Prompt
Original prompt

Source: cloudnativeengineer.substack.com · Giuseppe Santoro