Project Overview

Net7 is a SaaS platform built for Spanish freelancers who want to stop relying on a traditional accountant. For €7.99/month it covers the entire tax and invoicing cycle: create and send invoices, record expenses, manage clients and automatically simulate the mandatory quarterly tax forms (130, 303 and 349).

The competition (Holded, Quipu, Declarando, TaxDown) handles invoicing or taxes well, but rarely both in the same interface. Net7 integrates them in a single workflow designed for the individual freelancer who doesn’t have time to learn tax law.

Architecture: Two-app Monorepo

The project is made up of two independent applications with separate domains:

net7-app → app.net7.es — The SaaS application with authentication and all features
net7-web → net7.es — The marketing website, landing page and SEO blog

net7-app — The SaaS Application (Next.js)

Core Features

Full Invoicing

Create, edit, send and collect invoices with automatic numbering YYYY-NNN
Server-side professional PDF generation with react-pdf (rendered on the server, no browser dependency)
Credit notes (R-YYYY-NNN) with reason, reference to the original invoice and full or partial cancellation
VAT (21%, 10%, 4%, 0%) and income tax withholding (15%, 7%, 0%) configurable per profile
EU intra-community clients with automatic reverse charge (0% VAT, 0% withholding)
Reusable invoice templates to speed up creation

Expense Tracking

Record expenses with supported VAT, deductible/non-deductible category
Recurring expenses with a template+child model: the template acts as the expense for the creation month; children are generated automatically on each dashboard visit
Self-employed social security quota (RETA) auto-inserted monthly from the user profile

Client Management

National clients (NIF) and intra-community EU clients (ROI/VAT number)
Configurable payment terms per client with automatic due date calculation
Soft-delete to preserve invoice history without losing data

Quarterly Tax Simulator

Form 130 (Income Tax): annual cumulative calculation, 20% of net profit, deducting prior payments of the year
Form 303 (VAT): output VAT minus input VAT for the quarter; negative result is carried forward
Form 349 (Intra-community): summary of operations with EU clients grouped by VAT number
All data calculated automatically from the user’s real invoices and expenses
Save the form, mark as “filed” and generate a PDF summary

Dashboard & Metrics

Monthly KPIs: revenue, expenses, net balance and estimated tax to pay
Monthly revenue/expense chart (recharts)
Annual cumulative balance

Subscription & Payments with Stripe

Free Plan: 3 active clients, 5 invoices/month, no access to tax forms
Pro Plan (€7.99/month or €79.99/year): unlimited everything
Stripe checkout with redirect, customer portal to manage or cancel
Webhooks as the single source of truth for plan state: never updated manually
Contextual upgrade banner when the free plan limit is reached

Tax Reminder Emails

Opt-in in profile with configurable days in advance
Transactional emails with Resend (React template)
Token-protected cron job (/api/cron/tax-reminders/) with a deduplication table to avoid sending the same reminder twice

Notable Architecture Decisions

Server Actions exclusively for mutations — No mutation happens directly from client components; all writes go through Next.js Server Actions, simplifying authorization and eliminating unnecessary API endpoints.

React.cache() to deduplicate the session — getAuthUser() is called from multiple Server Components in the same request without duplicating Supabase queries, thanks to cache().

Server-side PDF without JSX in route handlers — The /api/pdf/[id] endpoint uses React.createElement() + renderToBuffer() explicitly because Next.js route handlers don’t have JSX compilation. The template component is separated so it can be reused in both contexts.

Plan limits enforced server-side — checkPlanLimit() is called in every Server Action before any insert. The client is never the only barrier protecting the plan limit.

Application-level RLS — All Supabase queries explicitly filter by the authenticated user’s user_id. While Supabase supports native RLS, this approach makes policies explicit and auditable in code.

E2E tests with conditional skipping — Playwright tests never fail due to empty data state or plan limits. They use test.skip() intelligently to adapt to the real environment state.

net7-web — The Marketing Website (Astro)

High-performance static site built with Astro 5. Its goal is to capture SEO traffic and convert it into app users.

SEO Blog (10 Articles)

The articles target the highest-volume searches in the segment, with quarterly spikes around tax filing deadlines:

How to fill in Form 130 step by step
How to fill in Form 303 step by step
Form 349: what it is and when to file it
Spanish freelancer tax calendar 2026
Deductible expenses for self-employed workers
How to create an invoice as a freelancer
Credit notes: when and how to issue them
Income tax withholding for freelancers: complete guide
Best invoicing software for freelancers 2026 (direct competitor comparison)
Freelancer without an accountant: is it possible? (anchor conversion article)

All include JSON-LD structured data (Article, SoftwareApplication), internal linking between posts and mid-article and final CTAs to the app.

Full Tech Stack

net7-app (Next.js)

Framework: Next.js 16 with App Router, Server Components and Server Actions
Database: Supabase (PostgreSQL + Auth + RLS)
UI: shadcn/ui + Radix UI + Tailwind CSS v4
Forms: react-hook-form + Zod v4
PDF: @react-pdf/renderer (server-side)
Charts: Recharts
Payments: Stripe (checkout, portal and webhooks)
Email: Resend
Testing: Vitest (unit) + Playwright (E2E)

net7-web (Astro)

Framework: Astro 5 (SSG, zero JS by default)
Styling: Tailwind CSS v4 + @tailwindcss/typography
Content: Astro Content Collections (typed Markdown)
SEO: automatic sitemap, RSS feed, structured JSON-LD