Use cases
Build payment apps with AI-assisted engineering
Invoicing, subscriptions, checkout, deposits — apps that move money, built with provider-hosted card handling, refund controls and an audit trail on every action.
Ciao is an enterprise AI-assisted engineering platform for building payment apps — invoicing, subscription billing, checkout and deposit collection — as real React, TypeScript and Supabase applications. Payment flows use the provider's hosted components through Ciao's one-click payments Block, so raw card data stays with the payment provider. Every change to payment logic passes Guardrails review, automated QA and live security testing, with an append-only audit trail behind each merge.
Published 2026-07-03 · Last updated 2026-07-03
The highest-stakes category of app
A payments app is any application where money changes hands: an invoicing tool, a subscription billing portal, a checkout, a donation platform, deposit collection for bookings. It is the category where a bug is not a visual glitch — it is a customer charged twice, a refund issued without authority, or a ledger that does not match the payment provider's records at month end.
That risk profile sets the requirements. Card data must stay with the payment provider, not your code. Refunds need permission tiers and reasons. Provider webhooks must reconcile against your own records, with mismatches surfaced instead of discovered at close. And every change to payment logic needs review you can point to later.
This is exactly the shape of work Ciao is built for. The payments Block wires provider-backed checkout in one step, and the delivery loop — Guardrails policies on the payments area, QA replays of charge and refund flows, security testing against the live app — treats payment code with the seriousness it deserves.
What a payments app actually requires
- Provider integration done right — Checkout, subscriptions and invoices through the payment provider's APIs and hosted components — raw card data never touches your code.
- A product and price catalog — Plans, one-off items, discounts and tax treatment defined once and referenced everywhere.
- Subscription lifecycle states — Trial, active, past due, canceled — mirrored from provider webhooks so your app and the provider never disagree about who is a customer.
- Dunning and retries — Failed payments enter a defined recovery path — retries, emails, grace periods — instead of silent churn.
- Refunds with controls — Permission tiers, amount limits, required reasons and an approval step above thresholds.
- Webhook reconciliation — Every provider event lands, is verified and is matched against your records — with an exceptions queue for mismatches.
- Receipts, invoices and tax fields — Numbered documents with the tax data your jurisdictions require, archived as issued.
- A money-movement log — Charges, refunds, credits and payouts recorded append-only, so finance can reconcile without asking engineering.
- Test and live separation — Test keys and live keys strictly separated by environment, so nobody test-charges a real card.
How a payments app build runs on Ciao
1. Describe the money flow
Who pays, for what, when, and what happens on failure — invoicing, subscriptions, deposits or checkout, in plain language.
2. Add payments in one step
The payments Block wires provider-backed checkout, webhooks and customer records with test keys first.
3. Model the catalog and lifecycle
Products, prices, subscription states and dunning paths land as schema and readable logic.
4. Build reconciliation from day one
Webhook handling with verification, matching against your ledger records and an exceptions queue — visible in the full-stack console.
5. Test with money-grade paranoia
QA replays charge, refund, failed-payment and webhook-replay paths; security testing probes access controls on the live app.
6. Govern the payments area
Guardrails treats payment logic as a protected zone — plain-English policies like "changes here require finance-approved review", enforced with a recorded trail.
7. Go live deliberately
Switch to live keys by environment, watch the first real transactions through Doctor, and keep rollback ready.
Security and governance checklist
- ✓ Card data captured by the payment provider's hosted components only
- ✓ Test and live provider keys separated by environment
- ✓ Refund permissions tiered, with limits and required reasons
- ✓ Webhook signatures verified; events reconciled against your own records
- ✓ Guardrails review recorded on every change to the payments area
- ✓ QA replays of charge, refund and failure paths before each publish
- ✓ Security scanning with vulnerabilities confirmed against the live app
- ✓ Append-only audit trail across prompts, merges, deploys and admin actions
Payments app variations
Invoicing app
Numbered invoices with tax fields, payment links, reminders and a receivables view that matches the provider's records.
Subscription billing portal
Plan changes, proration, dunning and cancellation flows mirrored from provider webhooks.
Donation platform
One-off and recurring giving with receipts, campaign attribution and exportable records for finance.
Deposit collection for bookings
Deposits and no-show fees tied to reservations, refunded by policy rather than discretion.
Usage-based billing
Metered consumption rated into invoices, with customers seeing the meter before the bill.
Client payment portal
Agencies and firms collecting retainers and project payments against milestones, in their own brand.
Payments requirements, covered
| Requirement | How Ciao covers it |
|---|---|
| Card data handling | Provider-hosted checkout components via the payments Block |
| Books that match the provider | Verified webhooks reconciled against append-only ledger records |
| Refund control | Permission tiers, limits, reasons and approval thresholds |
| Failed payments | Defined dunning paths with retries and customer messaging |
| Change control on payment code | Guardrails protected area with recorded human review |
| Confidence before go-live | QA replays of charge and refund flows; live security probes |
| Ownership of revenue data | Your Supabase database, your code — exportable at any time |
Frequently asked questions
How is card data handled?
Payment flows built with the payments Block use the provider's hosted checkout components, so raw card data is captured by the payment provider rather than passing through your application code. Ciao's security testing then probes the surrounding flows — access controls, session handling — against the live app.
Who can issue refunds?
Whoever your rules say — refund permissions are tiered by role, with amount limits, required reason codes and an approval step above thresholds. Every refund lands in the append-only money-movement log with the actor recorded.
How are changes to payment logic controlled?
Guardrails maps payment code into a protected business area. Plain-English policies — for example, that any change to charging or refund logic requires human review — are applied automatically, risky changes are flagged, and the review is recorded in an immutable trail behind the merge.
How do we know our records match the payment provider's?
Reconciliation is built into the app: provider webhooks are verified and matched against your own ledger records, and mismatches land in an exceptions queue with alerts instead of surfacing at month-end close.
Do we own the revenue data and the code?
Yes. Transaction records live in your Supabase database, the application is standard React and TypeScript exportable to your repo at any time, and customer code is never used to train models.
How do engagements start?
Payment apps are production programs from day one — they warrant a scoping conversation about providers, jurisdictions and controls. Serious development programs start at USD 10,000 per year; talk to sales to map your money flows first.