Field Invoicing Mobile Platform

Outcomes

Context

Invoices created days later lose money and trust — field issuance matters.

Challenge

Field teams needed to issue and manage invoices away from the desk — with reliable PDF output, email delivery, and authenticated API access.

Approach

We built a NestJS API with TypeORM, JWT auth, PDF generation, SendGrid mail, rate limiting, and AWS object storage patterns, paired with an Ionic Capacitor mobile client for on-the-go invoicing.

Architecture

NestJS API, MongoDB/TypeORM data layer, PDF service, email provider, AWS storage, Ionic Angular Capacitor app.

Scope

• —Invoice API
• —PDF generation
• —Email delivery
• —Mobile client
• —Document storage

Constraints

• —Document correctness
• —Mobile connectivity
• —Email deliverability

Solution highlights

• —PDF generation in the API domain
• —Mobile client for issuance, not only viewing
• —Mail + storage as first-class integrations

Technologies

Results

• —Mobile-capable invoicing workflows for field staff
• —PDF and email as built-in billing artifacts
• —Authenticated API with swagger-era documentation patterns
• —Storage for generated documents

Lessons learned

• —Mobile invoicing is a document pipeline, not a form.
• —Numbering and retries need explicit design.
• —Email deliverability is part of billing reliability.