The challenge
Anyone who's built their own home in the UK knows the VAT reclaim process. You're entitled to claim back VAT on eligible materials under HMRC's VAT431NB scheme, but actually doing it is a different story. Hundreds of receipts from dozens of suppliers. Manual data entry for every invoice. Complex eligibility rules about what qualifies and what doesn't. A six-month deadline from completion that catches people out. And a multi-page HMRC form that needs to be filled out perfectly.
Most self-builders either give up thousands of pounds in legitimate claims or spend weeks of their lives on paperwork. Our client wanted to fix that.
What we built
Build Manager is a three-service platform that automates the entire VAT reclaim workflow:
Smart receipt capture. Builders upload receipts through the web interface or simply forward them to a dedicated email address. The system accepts PDFs, photos, and scanned documents — whatever format they arrive in.
AI-powered data extraction. AWS Textract processes each receipt, extracting supplier details, VAT registration numbers, line items, amounts, and dates. The system handles the messy reality of real-world receipts — different formats, handwritten notes, partial scans. A supplier alias system learns to normalise OCR inconsistencies over time.
Automated compliance checking. Every receipt is validated against HMRC rules at the line-item level. Items are categorised, flagged for review if they need human judgement, and excluded if they clearly don't qualify. The system catches issues that would cause HMRC to reject a claim — missing VAT numbers, invalid dates, duplicate submissions.
Claim readiness dashboard. A real-time dashboard shows exactly where the claim stands — total spend, claimable VAT, percentage of receipts validated, items needing review, and countdown to the submission deadline. Builders can see at a glance what needs attention.
One-click form generation. When the claim is ready, the system pre-fills the official HMRC VAT431NB PDF with all claimant, property, and financial details, and generates a CSV export of all eligible invoices. What used to take days of form-filling takes seconds.
Architecture
Three independent services handle tenant management, receipt processing, and the admin frontend. Email ingestion uses SES inbound rules piped through SNS to a Lambda processor that parses MIME messages and triggers the OCR pipeline. File storage uses S3 with presigned URLs for secure access. The entire system is serverless, scaling automatically with demand.
The result
A process that typically takes self-builders weeks of evenings and weekends now takes hours. Receipt processing is near-instant. Compliance issues are caught early, not at submission. And the claim form — the part everyone dreads — generates itself. For a typical self-build with 300–500 receipts and a VAT claim worth £30,000–£60,000, that's a meaningful amount of money recovered with a fraction of the effort.