OpenChainGraph Suite · ART-294 · e-invoicing

E-Invoice VAT Calculation Verifier

Recomputes line VAT, per-category tax subtotals, tax total, and grand total from an invoice's line items under a supplied rounding convention, then compares the result against the document-asserted amounts. Reverse-charge and zero-rate categories are treated as zero VAT regardless of any stated rate. Verifies arithmetic consistency only, not the legal correctness of the underlying rate. Zero network.

E-InvoicingMulti-rateReverse-Charge AwareZero PIIW3C VC §13.11
🔒 All inputs are processed locally in your browser. No data is transmitted. Do not enter real personal data — use synthetic or anonymised inputs only.
Scope
Middle node of the einvoice-validation-pipeline chain (art-293→294→295→296). Verifies internal arithmetic consistency only; does not assert the applied VAT rate is statutorily correct. See einvoice-validation-pipeline chain.
Presets
Invoice Inputs
Result
Execution Hash & §4 Artifact
SHA-256 execution hash (JCS canonical, RFC 8785):

      

        
        
        
        
        
      

    

  


  
  

    

  







  

    
Ask your agent

    
  

  
Copy this paragraph into Claude, OpenClaw, or any MCP-aware agent to run this exact tool, with this sample, and verify the artifact.

  
Run the AINumbers MCP tool `verify_einvoice_vat_calc`. Task: Recompute an e-invoice's line VAT, per-category tax subtotals, tax total, and grand total from its line items under a supplied rounding convention, and compare against the document-asserted amounts.
Call it with arguments: {"policy_parameters":{"document":{"line_items":[{"line_id":1,"net_amount":1000,"vat_category":"S","vat_rate_pct":19},{"line_id":2,"net_amount":500,"vat_category":"Z","vat_rate_pct":0}],"tax_subtotals_asserted":[{"vat_category":"S","vat_rate_pct":19,"taxable_amount":1000,"tax_amount":190},{"vat_category":"Z","vat_rate_pct":0,"taxable_amount":500,"tax_amount":0}],"grand_total_asserted":1690,"tax_total_asserted":190},"rounding":{"method":"half-up","granularity":"per-line"}}}
Verify before trusting: call `verify_execution_hash` on mcp.ainumbers.co (https://mcp.ainumbers.co/mcp) with the parameter `claimed_hash` set to the returned `execution_hash`, passing the full artifact the run returned (the object containing `policy_parameters` + `output_payload` + `execution_hash`; equivalently `policy_parameters` + `output_payload` with `claimed_hash`), not the bare hash string.
Return the ledger link https://ledger.ainumbers.co/ so a human can re-verify without contacting us.
PII rule: All inputs are processed locally in your browser. No data is transmitted. Do not enter real personal data — use synthetic or anonymised inputs only.
Open the tool with the sample prefilled: https://ainumbers.co/chaingraph/art-294-einvoice-vat-calc-verifier.html#p=v1.H4sIAAAAAAAA_wHGATn-eyJkb2N1bWVudCI6eyJsaW5lX2l0ZW1zIjpbeyJsaW5lX2lkIjoxLCJuZXRfYW1vdW50IjoxMDAwLCJ2YXRfY2F0ZWdvcnkiOiJTIiwidmF0X3JhdGVfcGN0IjoxOX0seyJsaW5lX2lkIjoyLCJuZXRfYW1vdW50Ijo1MDAsInZhdF9jYXRlZ29yeSI6IloiLCJ2YXRfcmF0ZV9wY3QiOjB9XSwidGF4X3N1YnRvdGFsc19hc3NlcnRlZCI6W3sidmF0X2NhdGVnb3J5IjoiUyIsInZhdF9yYXRlX3BjdCI6MTksInRheGFibGVfYW1vdW50IjoxMDAwLCJ0YXhfYW1vdW50IjoxOTB9LHsidmF0X2NhdGVnb3J5IjoiWiIsInZhdF9yYXRlX3BjdCI6MCwidGF4YWJsZV9hbW91bnQiOjUwMCwidGF4X2Ftb3VudCI6MH1dLCJncmFuZF90b3RhbF9hc3NlcnRlZCI6MTY5MCwidGF4X3RvdGFsX2Fzc2VydGVkIjoxOTB9LCJyb3VuZGluZyI6eyJtZXRob2QiOiJoYWxmLXVwIiwiZ3JhbnVsYXJpdHkiOiJwZXItbGluZSJ9fYBA87PGAQAA