Shafer Law Payments
Architect & sole engineer · 2026A production billing and online-payment system for a law firm
Next.jsTypeScriptStripePrismaPostgreSQLClerkWebhooksVercel
Invoicing and card/ACH payments for a law firm, engineered for the correctness and audit standards that money and bar-association compliance demand.
> The_Problem
A firm needed to invoice clients and take payments online without exposing itself to double-charges, lost payments, or an audit trail that couldn't stand up to bar-association review.
> What_I_Built
- ▸Stripe Checkout (cards, ACH, Apple/Google Pay), token-gated public payment links, and automated email receipts.
- ▸Signature-verified, idempotent webhooks with two-layer deduplication so a replayed or duplicated event can never double-apply.
- ▸Atomic invoice numbering, integer-cent accounting (no floating-point money), and ACH payout reconciliation that ties bank transfers back to individual payments.
- ▸An append-only audit log designed for bar-association review, with card data kept entirely off the application (PCI SAQ-A).
> Outcome
- ✓Correct-by-construction money handling: no double-charges, deterministic reconciliation, full audit trail.
- ✓Deployed and handling real client payments.