Bookkeeping for Plumbers: A Complete Guide for Australian Plumbing Businesses

Why Bookkeeping Matters for Plumbing Businesses

Plumbing is one of Australia's largest trade sectors, with more than 75,000 licensed plumbers operating across residential, commercial, and industrial markets. Most are either sole traders or small businesses employing a handful of employees and apprentices.

The financial side of a plumbing business is more complex than many owners realise. You are managing job costs, tools and equipment, multiple vehicles, materials purchased on account, apprentice wages, super obligations, and potentially subcontractor relationships. Without a solid bookkeeping system, it is easy to lose track of which jobs are profitable and which are quietly draining your margins.

This guide walks through the key bookkeeping areas every Australian plumbing business owner needs to understand.

Setting Up Your Chart of Accounts

The chart of accounts is the backbone of your bookkeeping system. For a plumbing business, your accounts should reflect the key cost and income categories you actually work with.

Income Accounts

• Residential plumbing (service and repair)
• New construction and rough-in
• Commercial plumbing
• Drainage and sewerage
• Gas fitting
• Maintenance contracts and call-outs

Separating these income streams lets you track which work type generates the most revenue and margin. This is the starting point for smarter pricing decisions.

Expense Accounts

• Materials and supplies (pipes, fittings, fixtures)
• Subcontractor labour
• Tools and equipment (small tools vs capital equipment)
• Vehicle operating costs (fuel, rego, insurance, repairs)
• Uniforms and PPE
• Licensing and industry memberships
• Apprentice wages
• Superannuation
• Public liability and professional indemnity insurance
• Marketing and website

Asset Accounts

• Vehicles (ute, van)
• Trailer
• Power tools and test equipment
• Computers and mobile devices

Most plumbing businesses should have at least 25 to 30 account codes to provide meaningful financial visibility without creating unnecessary complexity.

Job Costing: Knowing Your Real Margins

One of the most important, and most overlooked, aspects of bookkeeping for plumbers is job costing. Job costing lets you track the actual cost of each job against what you quoted and invoiced, so you can see precisely which jobs are making money and which are breaking even or worse.

What to Track Per Job

• Materials purchased for the job
• Hours spent (your own time and any employees)
• Subcontractor costs
• Vehicle costs if significant (long-distance travel)
• Permit fees

Setting Up Job Tracking in Xero

Xero's tracking categories feature allows you to tag income and expense transactions against a specific job or project. This is not as sophisticated as dedicated job management software (like Fergus, ServiceM8, or Simpro), but for smaller plumbing operations it can provide useful job-level visibility without additional cost.

For larger businesses, integrating Xero with a field service management platform is well worth the investment. These platforms handle scheduling, quoting, invoicing, and time tracking, then push the financial data through to Xero automatically.

GST for Plumbers

Plumbing businesses with turnover above $75,000 per year must register for GST and lodge a BAS. Most plumbing income is taxable at 10% GST, with a few exceptions.

Standard GST Treatment

• All labour charges: 10% GST
• Materials supplied to customers: 10% GST
• Most subcontractor payments: subject to GST if the subcontractor is GST-registered

Input Tax Credits

You can claim back the GST paid on business purchases:

• Materials bought from trade suppliers
• Tools and equipment
• Vehicle fuel and servicing
• Uniforms
• Business insurance

The key is keeping tax invoices for every purchase. The ATO requires a valid tax invoice for any purchase over $82.50 (including GST). Fuel receipts, hardware store dockets, and supplier invoices all qualify, provided they show the supplier's ABN and the GST amount.

Cash vs Accruals BAS

Many plumbers lodge their BAS on a cash basis, meaning you report GST when you actually receive or make payment rather than when you invoice or receive a bill. This is simpler for sole traders and aligns your BAS to your actual cash position.

If you move to accruals, be aware that you will report GST on invoices raised even before payment arrives, which can create cash flow timing issues. Discuss with your accountant or bookkeeper which method suits your situation.

Handling Subcontractors

Using subbies is common in plumbing, especially for drain relining, gas work outside your licence, or covering overflow capacity. Subcontractor payments have specific ATO requirements.

Taxable Payments Annual Report (TPAR)

Plumbing businesses that pay subcontractors must lodge a Taxable Payments Annual Report (TPAR) with the ATO by 28 August each year. This report discloses the total amount paid to each subcontractor and their ABN.

If you miss this reporting obligation, the ATO can impose penalties and may disallow the deduction for those payments.

What you need to collect from each subcontractor:

• Full legal name or business name
• ABN
• Address
• Total gross amount paid during the financial year
• Total GST included in payments

Xero can generate a draft TPAR report if you have been recording subcontractor payments correctly throughout the year. Set up a dedicated expense account for subcontractor labour to make this process easy.

Withholding for No-ABN Subcontractors

If a subcontractor does not provide their ABN, you are required to withhold 47% of any payment and remit it to the ATO. This is the no-ABN withholding rule. It applies even if the subcontractor is a legitimate business. Always get ABNs before paying subbies.

Vehicle and Equipment Expenses

Vehicles and tools are major cost categories for plumbing businesses and offer significant tax deduction opportunities, provided they are handled correctly.

Vehicles

You can claim vehicle expenses in one of two ways:

Logbook method: Keep a logbook for at least 12 weeks to establish the business use percentage of the vehicle. You can then claim that percentage of all vehicle running costs, including fuel, insurance, registration, servicing, and depreciation.

Cents per kilometre: Claim a flat rate per business kilometre driven. In the 2025-26 financial year, the ATO rate is 88 cents per kilometre. This method is simpler but caps your deduction and works best for lower-mileage situations.

Most plumbers with a dedicated work ute or van will benefit from the logbook method, particularly if the vehicle is predominantly used for work.

Tools and Equipment

For tools costing under $20,000, most small plumbing businesses can use the instant asset write-off scheme to claim the full cost of the tool as a deduction in the year of purchase. This applies to power tools, test equipment, trailers, and similar assets.

For larger equipment or vehicles, standard depreciation rules apply unless the instant asset write-off threshold applies. Your accountant can advise on current thresholds for the relevant financial year.

Keep all purchase receipts for tools. The ATO can and does ask for substantiation of equipment claims.

Managing Payroll for Plumbers

If you employ apprentices, tradespeople, or admin staff, payroll is a critical part of your bookkeeping.

Award Rates

Plumbers are covered by the Plumbing and Fire Sprinklers Award 2020. Pay rates vary by classification (C10 through C4) and experience level. Make sure your payroll software is configured with the correct award rates and that you are paying at least the minimum for each classification.

Superannuation

From 1 July 2025, the superannuation guarantee rate is 12%. You must pay super for all eligible employees by the quarterly super due dates (28 October, 28 January, 28 April, and 28 July).

Late super payments attract the superannuation guarantee charge, which is not tax-deductible and includes an interest component. Set a calendar reminder for each due date.

Single Touch Payroll (STP)

All Australian employers must report payroll to the ATO in real time via Single Touch Payroll. If you use Xero Payroll, STP is built in and reports are sent automatically each pay run. Make sure you are using STP Phase 2, which is the current version, and that your payroll software is configured correctly.

Common Bookkeeping Mistakes in Plumbing Businesses

Mixing Personal and Business Finances

This is the number one mistake. If you use the same account for business and personal spending, unpicking the two is time-consuming and error-prone. Open a dedicated business bank account and business credit card.

Not Recording Cash Jobs

Every job you complete and get paid for, including cash payments on small residential jobs, is taxable income. The ATO uses data matching to identify businesses with income inconsistencies relative to industry benchmarks. Failing to declare cash income is tax evasion, not a grey area.

Falling Behind on Reconciliation

If your bank accounts are not reconciled monthly, your BAS figures will be wrong, your profit and loss will be misleading, and you will not know how your business is actually performing. Make reconciliation a weekly habit, not a quarterly scramble.

Claiming Personal Expenses as Business Expenses

Tools used for personal projects, meals with family members, and holidays are not business deductions. Claiming personal items as business expenses is a common audit trigger.

Missing Superannuation Deadlines

Late super payments attract the super guarantee charge, which is not deductible and cannot be offset against future super contributions. Set payment dates as recurring calendar events and pay before the deadline, not on it.

How SortBooks Helps Plumbing Businesses

SortBooks connects to your Xero file and automatically categorises transactions, validates GST treatment, and flags anomalies before they become problems. For a plumbing business, this means:

• Materials, fuel, and tool purchases categorised correctly as soon as they clear the bank
• Subcontractor payments flagged for TPAR tracking
• Vehicle expenses separated from personal spending (if you flag personal items for review)
• BAS-ready figures without a manual reconciliation sprint before each quarter

Combined with a good job management platform feeding data into Xero, SortBooks helps plumbing businesses maintain clean books with minimal manual effort.

Final Thoughts

Running a plumbing business well means knowing your numbers. That starts with a clean chart of accounts, accurate job costing, proper GST handling, and staying on top of payroll and super obligations.

The paperwork side of plumbing does not have to be painful. With the right tools and a consistent routine, most plumbing businesses can maintain accurate books in less than two hours per week. The return on that investment, in tax savings, better pricing decisions, and peace of mind at BAS time, is well worth it.