Estimate, invoice, get paid — on the web and in your pocket.

The challenge

Small businesses and freelancers don't want accounting software — they want to send a professional invoice, get paid quickly, and stay organized at tax time, from whatever device is in front of them. The brief was a genuinely simple product that still covers the full money-in / money-out loop and lets each business get paid through its own payment accounts.

What we built

• Invoices & estimates. One engine drives branded invoices and estimates with line-item tax, discounts and currency; a live status lifecycle (Open → Partially Paid → Paid, Overdue; estimates Approved/Declined/Expired); one-click estimate-to-invoice conversion; server-side A4 PDF; and emailed delivery with BCC-to-self.
• Get paid online. Customers open a token-secured public link — no login — and pay inline by card via Stripe.js (with card-on-file for repeat charges and partial payments) or PayPal, or the business logs a manual/offline payment. Estimates can be approved or declined right from the same link.
• Bring-your-own gateways. Each business connects its own Stripe keys and PayPal email in Settings — credentials resolved per tenant, no shared marketplace account — so money flows straight to them.
• Expenses & reporting. Expense tracking by merchant and category feeds a sales dashboard and a report library — Sales, Payments, Expenses, Tax and Profit, monthly or quarterly — each exportable to CSV and emailable straight to an accountant.
• Recurring billing & subscriptions. Businesses bill their own customers on a schedule through Stripe Subscriptions, while Invoice+'s freemium SaaS tiers gate premium features — with plan changes also originating from App Store / Google Play in-app purchases, validated via a signed Apple JWT webhook.
• Multi-currency, tax & localization. Per-business and per-client currency (USD/CAD), custom named tax rates applied per line, and preferences for language, timezone, date format, fiscal year and branding.

Under the hood

A single ASP.NET Core MVC app on .NET 10 hosting the tenant app, admin console, marketing site and public pay pages, on EF Core 10 over SQL Server. The front end was modernized to Vue 3 against a JSON API, with Stripe.js for payments, DinkToPdf for PDF generation, and SendGrid for delivery. The same codebase powers the native iOS and Android apps through mobile-optimized webview flows.

Outcome

One low-complexity product covering the whole estimate → invoice → payment → reporting loop, across web and mobile, with every business paid through its own gateways — now modernized to a .NET 10 / Vue 3 stack.