Read the six PDFs in cases/01-invoice/input. Build an Australian invoice register with source file/page, document type, supplier identity, supplier ABN, buyer identity, invoice number, issue date, due date, purchase order, currency, subtotal excluding GST, GST rate, GST shown, total including GST, calculated GST, calculated total, differences, duplicate status and review issues. Normalise dates to real date values displayed as DD/MM/YYYY. Retain all source rows but count each supplier/invoice/currency key once, using the first filename. For this base set, every line is specified as taxable at 10% GST and amounts are AUD. Check GST = round(subtotal ex GST * 10%, 2), total = subtotal + GST, and GST = total / 11 for these wholly taxable invoices. Do not apply those formulas blindly to GST-free, input-taxed, mixed, non-GST-registered or overseas purchases. Extract printed ABNs as text. Check the 11-digit format and modulus-89 checksum locally, then distinguish checksum success from registration verification. A heading saying TAX INVOICE is not sufficient evidence of validity or GST-credit entitlement. Keep the missing due date and PO blank; distinguish operational missing fields from mandatory tax-invoice information. Produce invoice-register.xlsx and review-notes.md with linked summary formulas. Do not invent identifiers, assert registration, approve GST credits or make payments. Do not use the optional extensions unless specifically requested. Use supplied files and local tools only; do not call paid model/OCR APIs or upload documents. Save outputs in a new folder in system Downloads without overwriting.
