Accounting for construction and trades businesses in NZ

Published Friday 11 September 2026

Table of contents

• What is construction accounting?
• Common accounting methods for construction businesses
• Job costing for construction projects
• Managing subcontractor payments and withholding tax
• GST obligations for construction businesses in NZ
• Bookkeeping best practices for builders and tradies
• Payroll and employee obligations
• Cash flow management for construction businesses
• Choosing accounting software for your construction business
• Simplify your construction finances with Xero
• FAQs on construction accounting in NZ

Key takeaways

• Construction accounting in NZ goes beyond standard bookkeeping: you'll need project-based tracking, job costing, and careful management of Goods and Services Tax (GST), withholding tax, and Inland Revenue Department (IRD) compliance.
• Choosing the right accounting method, whether cash-basis, accrual, or percentage of completion, affects how you recognise income and manage tax obligations across long-running projects.
• Accurate job costing helps you monitor profit margins on every project, spot cost overruns before they escalate, and build more competitive quotes using real historical data.
• Cloud accounting software can simplify invoicing, bank reconciliation, payroll, and financial reporting, giving you more time on the tools and less time buried in paperwork.

What is construction accounting?

Construction accounting in NZ is the process of tracking income, expenses, and profitability across individual projects rather than treating your business as a single revenue stream. It's built for the way construction and trades businesses actually work: multiple jobs running at once, each with their own materials, labour, subcontractors, and timelines.

How construction accounting differs from standard accounting

Standard accounting typically records income and expenses as they flow through the business. Construction accounting adds a layer of complexity because your revenue is tied to specific projects that can span weeks, months, or even years.

You're dealing with progress billing, where you invoice for work completed in stages rather than at the end. You've got retentions held back by clients until defects liability periods expire. And you're juggling multiple cost categories per project: materials, labour, subcontractor costs, equipment hire, and overheads.

For NZ construction companies and contractors, this project-based approach isn't optional. Without it, you can't see which jobs are making money and which ones are eating into your margins.

Common accounting methods for construction businesses

There are three main accounting methods used in the construction industry, and the one you choose affects how you recognise income and when you pay tax.

Cash-basis accounting

With cash-basis accounting, you record income when you receive payment and expenses when you pay them. It's straightforward and works well for smaller operations or businesses that complete short-duration jobs. However, it doesn't give you a clear picture of money owed to you or bills you haven't paid yet.

Accrual accounting

Accrual accounting records income when you earn it and expenses when you incur them, regardless of when cash changes hands. This gives you a more accurate view of your financial position at any point in time. Most NZ businesses above the $60,000 GST registration threshold use accrual accounting, and it's generally required for accurate GST reporting.

Percentage of completion method

The percentage of completion method (PCM) recognises revenue proportionally as work progresses. You calculate the percentage complete by dividing costs incurred to date by total estimated costs.

For example, if you've spent $350,000 on a project with total estimated costs of $700,000, you're 50% complete. On a $1,000,000 contract, you'd recognise $500,000 in revenue at that point.This method suits long-running projects because it aligns your reported revenue with work actually done, rather than waiting until the job is finished.

Job costing for construction projects

Job costing tracks the costs of each construction project individually, giving you a clear picture of profitability on every job. For businesses running multiple projects at once, it's essential for understanding where your money is going and whether your quotes are accurate.

What to track in a job cost report

A solid job cost report captures every expense tied to a specific project. At a minimum, you should be tracking:

• Direct materials: timber, concrete, steel, fittings, and any other supplies purchased for the job
• Direct labour: wages for employees working on that project, including overtime
• Subcontractor costs: payments to subcontractors, including any withholding tax obligations
• Equipment hire and fuel: plant and machinery costs allocated to the job
• Overhead allocation: a portion of your fixed costs (rent, insurance, vehicle running costs) assigned to each project
• Permits and compliance costs: building consents, inspection fees, and health and safety requirements

Using job costing to improve profitability

The real value of job costing comes from comparing your quoted costs against actual costs as the project progresses. If you quoted $45,000 for labour on a renovation and you're already at $38,000 with three weeks to go, you can see the overrun coming and adjust.

Review your job cost reports regularly. Weekly checks help you catch problems early, while end-of-project reviews build a library of actual costs you can use to sharpen future quotes. Over time, this data becomes one of your most valuable business assets.

Managing subcontractor payments and withholding tax

If you hire subcontractors, you've got specific tax obligations to manage. Getting this wrong can mean penalties from the IRD, so it's worth understanding the rules.

In NZ, payments to subcontractors are classified as schedular payments. Before you make the first payment, your subcontractor needs to complete an IR330C tax rate notification form. This tells you the withholding tax rate to deduct.

The standard withholding rate is 20%, but subcontractors can apply to the IRD for a tailored rate based on their circumstances. If a subcontractor doesn't provide an IR330C, you're required to withhold at the no-notification rate, which is higher.

You need to deduct the correct withholding tax from each payment and pass it on to the IRD. If your subcontractors are GST-registered, their invoices will include GST, and you can claim that GST back on your return.

Keep records of every subcontractor payment, the IR330C forms you've received, and the withholding tax you've deducted. The IRD requires you to hold these records for a minimum of seven years.

GST obligations for construction businesses in NZ

GST is a significant part of managing your construction finances. Understanding when and how to register, file, and claim is essential for staying compliant and avoiding costly errors.

You must register for GST once your turnover reaches $60,000 in any 12-month period (or you expect it to). The current GST rate as of 2026 is 15%. You can choose to file your returns monthly, two-monthly, or six-monthly, depending on your turnover and preferences. Businesses with higher turnover often find monthly filing easier to manage because it smooths out cash flow.

Construction businesses need to pay special attention to GST on progress claims. You're required to account for GST when you issue a progress claim, not when the client pays it. The same applies to retentions: you account for the GST on the full invoice amount even though a portion is held back.

Common GST mistakes in construction include forgetting to claim GST on materials purchased for a job, mixing up the timing of GST on progress claims, and not keeping adequate records. If you're registered for GST, make sure you're tracking every business expense and claiming what you're entitled to.

Bookkeeping best practices for builders and tradies

Good bookkeeping habits make everything else easier: your tax returns, your job costing, your cash flow forecasting, and your conversations with your accountant. The key is building routines that work around a busy schedule on site.

Start by separating your personal and business bank accounts if you haven't already. This alone saves hours at tax time and gives you a cleaner view of your business finances.

Capture receipts on the day you get them. Use your phone to photograph receipts and store them digitally. Paper receipts fade, get lost in ute consoles, and end up going through the wash. Cloud-based tools can pull in bills and receipts automatically, so you're not manually entering data at the end of the month.

Reconcile your bank transactions regularly. Matching your bank feed to your accounting records weekly, rather than monthly, means you'll catch errors and missing transactions before they become problems.

Tracking project costs in real time

Set up cost codes or categories for each project so you can see exactly where money is being spent. This ties directly into your job costing and gives you up-to-date profitability data without waiting for month-end.

If you're running cloud accounting software with job costing features, you can tag expenses to specific projects as they happen. Mobile access means you or your team can log costs from site, keeping your data current and reducing the end-of-month scramble.

Payroll and employee obligations

Running payroll in the construction industry comes with its own set of requirements. If you've got employees, these are the key obligations to manage:

• PAYE (Pay As You Earn): You're responsible for deducting income tax from your employees' wages and paying it to the IRD. You need to file employment information with the IRD within two working days of each payday, which is known as payday filing.
• KiwiSaver: As an employer, you're required to contribute a minimum of 3.5% of each eligible employee's gross pay to their KiwiSaver fund. You also need to deduct the employee's own contribution and pass both amounts on to the IRD.
• Employer superannuation contribution tax (ESCT): You'll pay ESCT on your KiwiSaver employer contributions. The rate depends on each employee's earnings.
• Accident Compensation Corporation (ACC) levies: Construction businesses typically pay higher ACC levies than businesses in other industries because of the higher risk profile. These levies fund workplace injury cover, so they're a non-negotiable cost of operating in the trades.
• Holiday pay: Managing holiday pay for employees on variable hours or project-based work requires attention. If your employees' hours vary significantly, you may need to calculate holiday pay based on either ordinary weekly pay or average weekly earnings over the past 52 weeks, whichever is greater.

Using payroll software that handles PAYE, KiwiSaver, and payday filing automatically can save you significant time and reduce the risk of errors.

Cash flow management for construction businesses

Cash flow is consistently one of the most significant financial challenges for construction businesses. Long payment cycles, retentions, and the upfront cost of materials create gaps between spending money and receiving it.

Progress billing helps bridge this gap. Rather than waiting until a project is complete, you invoice for work done at agreed milestones. Setting clear payment terms and issuing invoices promptly keeps cash moving through your business.

Construction legislation

The Construction Contracts Act 2002 provides important protections for construction businesses in NZ. It establishes default payment terms, gives you the right to suspend work for non-payment, and provides an adjudication process for payment disputes. Understanding your rights under this legislation can make a real difference when clients are slow to pay.

Retentions

Retentions are another cash flow consideration. It's common for clients to hold back a percentage (typically 5% to 10%) of each progress payment until the project is complete and any defects are remedied. While retentions are standard practice, they can tie up substantial amounts of cash across multiple projects. Track retentions separately in your accounts so you know exactly how much is being held and when it's due for release.

Forecasting

To manage cash flow across multiple projects, forecast your costs and expected payments for each job on a weekly or fortnightly basis. Knowing when large material orders are due versus when client payments will land helps you avoid shortfalls and make better decisions about when to take on new work.

Choosing accounting software for your construction business

The right accounting software can transform how you manage your construction finances. When you're evaluating options, look for features that match the way your business actually operates.

• Job costing and project tracking: You need the ability to assign income and expenses to individual projects so you can see profitability at a glance.
• Invoicing and progress billing: Look for software that lets you create professional invoices, set up progress claims, and track what's outstanding.
• Bank feeds and reconciliation: Automatic bank feeds pull your transactions into your accounting software daily, making reconciliation faster and more accurate.
• Payroll: If you've got employees, built-in payroll that handles PAYE, KiwiSaver, payday filing, and holiday pay calculations saves you running a separate system.
• Mobile access: Construction work happens on site, not at a desk. Choose software you and your team can access from a phone or tablet.
• Integration with other tools: Your accounting software should connect with the other tools you use, whether that's project management, estimating, or scheduling software.

Cloud accounting software gives you the advantage of real-time data, automatic updates, and access from anywhere. For businesses running 20 or more employees and multiple projects, it can significantly reduce the manual work involved in month-end reporting and financial management.

Simplify your construction finances with Xero

Managing the finances of a construction or trades business doesn't have to mean late nights buried in spreadsheets. Xero brings your invoicing, bank reconciliation, job costing, payroll, and financial reporting into one place, so you can see how your business is tracking without the manual admin.

Whether you're managing subcontractor payments, staying on top of GST, or trying to get a clear view of profitability across projects, Xero gives you the tools to stay in control.

Ready to spend less time on the books and more time on the tools? Get one month free.

FAQs on construction accounting in NZ

Here are answers to some common questions about managing accounting for construction and trades businesses in New Zealand.

Do construction businesses need a specialised accountant?

It's not a legal requirement, but working with an accountant who understands the construction industry is a significant advantage. They'll be familiar with job costing, progress billing, retentions, and the specific tax obligations that apply to your sector.

What records do construction businesses need to keep in NZ?

You're required to keep financial records for a minimum of seven years. This includes invoices, receipts, bank statements, employment records, subcontractor IR330C forms, and GST returns. Digital records are acceptable as long as they're accessible and accurate.

How often should I review my job costing reports?

Review job costing reports at least weekly for active projects. This lets you catch cost overruns early and make adjustments before they eat into your margins. At the end of each project, do a thorough review to compare actual costs against your original quote.

What's the difference between job costing and project accounting?

Job costing focuses specifically on tracking the costs associated with a single project to determine its profitability. Project accounting is broader; it includes job costing but also covers revenue recognition, billing, and financial reporting at the project level. For most construction businesses, the two terms are used interchangeably.