Every detail in its place.
The operating challenge
A finance team handles supplier invoices and statements through shared inboxes and spreadsheets. Staff extract the same fields, compare purchase orders and receiving records, and investigate discrepancies before posting.
The costliest part is often the exception: a duplicate invoice, unfamiliar supplier, missing receipt, or changed bank details. The system must distinguish data preparation from financial authorization.
A workflow with a clear next step
01 / Capture and deduplicate
Store the invoice source and detect duplicates using supplier, invoice number, amount, and a document hash.
02 / Extract fields
Read the supplier, invoice reference, currency, dates, tax, totals, and line items with source evidence.
03 / Validate records
Use deterministic arithmetic and supplier-master checks. Compare invoice, purchase order, and receiving records where applicable.
04 / Prepare the exception
Flag missing receipts, price variances, currency conflicts, and changed banking information for finance.
05 / Approve the posting
An authorized reviewer approves a draft accounting entry. Revalidate the source records before posting.
06 / Reconcile and report
Read back the posted record, track unresolved items, and preserve an audit trail. Payment remains a separate authorized process.
Architecture & controls
Approved invoice mailbox → OCR → supplier and PO APIs → accounting draft integration → Postgres review and event records. Accounting rules are encoded and reviewed by the client’s finance owner.
- No autonomous payments or supplier bank-detail changes.
- Segregate invoice preparation, approval, and payment authority.
- Use decimal-safe arithmetic and explicit currency handling.
- Block stale approvals, duplicate posting, and unsupported supplier changes.
When things do not go to plan
A changed bank account is routed to the existing independent verification process. Missing receiving records or tax ambiguity are held for review. Accounting API failures create bounded retries and reconciliation alerts; a retry must not create a second posting.
The automation boundary: The system prepares finance work. Authorized finance staff retain accounting judgment, supplier verification, posting approval, and payment control.
Evaluation, before expansion
Test duplicate PDFs, revised invoice numbers, credit notes, multi-currency cases, rounding, tax discrepancies, partial receipts, malicious document instructions, and API timeouts after a successful write. Finance reviews both field quality and accounting treatment.
| Measure | What we measure | Proposed criterion |
|---|---|---|
| Preparation time | Eligible invoice packets | Target: 35% below baseline |
| Duplicate detection | Representative duplicate and revised invoice tests | Gate: all seeded duplicates flagged |
| Authorization | Payments and bank-detail changes | Gate: never executed by this workflow |
Targets are agreed with the process owner after measuring representative current work. A pilot also records error rates, review effort, operating cost, and exceptions. Released staff capacity is not automatically a cash saving.
Rollout & handover
Move through offline evaluation, shadow mode, and operator-assisted work before considering a limited automatic path. Each phase has a named owner, stop conditions, and a manual fallback. The approved scope determines the delivery schedule.
What the engagement would deliver
- Invoice capture and duplicate controls
- Source-linked extraction
- Matching and exception rules
- Accounting draft and approval workflow
- Reconciliation report and finance runbook
The final handover includes client-owned access, configuration or source, known limitations, evaluation cases, and recovery instructions. Third-party subscriptions and ongoing support are agreed separately.
Technical references
These sources inform design considerations. They do not validate a deployed Tern & Loom project or establish vendor partnership.
AWS: Amazon Textract best practices ↗
Supabase: row-level security ↗
Research reviewed 20 October 2026.