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Automating Invoicing for a UK Construction Company with QuickBooks

Project Overview

Organization

A growing construction company

Industry

Construction

Challenge

Manual invoice creation and payment tracking across systems

Stack

QuickBooks Online API, n8n, OAuth2, Webhooks

Products / Services Used

  • API Integration
  • Workflow Automation
  • Payment Tracking
  • QuickBooks Online API
  • n8n
  • OAuth2
  • Webhooks

This client is a growing UK construction company running 50+ jobs a week.

Every invoice was created by hand in QuickBooks Online, the accounts team keyed in customer details, line items, and amounts for each job, then tracked payment status across spreadsheets, emails, and QuickBooks. At 15–20 minutes per job, the repetitive copy-paste work added up to a full working day a week.

The brief: connect the systems so invoices create themselves and payment status updates themselves, with zero manual entry.

Performance Insights

Key results for the client

15-20 min

Saved per job (previously manual entry)

50+

Jobs per week automated end-to-end

1 Day/Week

Of accounts team time reclaimed

Client Objectives

The challenges the client faced

1.
Manual invoice creation in QuickBooks

The accounts team created every invoice by hand in QuickBooks Online, entering customer details, line items, and amounts manually for each job.

2.
Copy-paste between systems

Every new job meant 15–20 minutes of copying data between the job-management workflow and QuickBooks, across 50+ jobs a week.

3.
Payment status scattered across spreadsheets

There was no single source of truth for payment status — the team chased updates across spreadsheets, emails, and QuickBooks separately.

4.
A full working day lost to data entry

At 50+ jobs a week, the cumulative manual effort consumed an entire working day that could have gone toward higher-value work.

Mavlers Strategy

How we automated invoicing end to end

1.
Connected QuickBooks Online via OAuth2

Set up secure OAuth2 authentication with QuickBooks Online, ensuring the integration met Intuit’s production API requirements from day one.

2.
Built webhook listeners for real-time payment events

Payment status updates now flow in real time via webhooks - no more checking QuickBooks manually or updating spreadsheets.

3.
Automated customer creation and invoice generation

The moment a job is logged, the pipeline creates the customer (if new), generates the invoice with the correct line items, and sends it with zero manual input.

4.
Took it through sandbox to production

Built and tested in Intuit’s sandbox environment, secured approved production API keys, and deployed the full integration on the client’s own n8n Cloud instance.

Results

What the client achieved

‍

‍

Mavlers’ work across APIs, AI automation workflows, website development, and general responsiveness has been consistently strong. Overall, we’re very happy with the team’s support and the quality of work delivered.

Sandra Field
Operations Director

Plant & Machinery Company

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