Bookkeeping for Construction: Job Costing & Compliance

Why Construction Bookkeeping Is Different

Construction businesses face bookkeeping challenges that most other industries never encounter. Every project is unique, costs shift constantly, and revenue recognition follows progress rather than simple invoicing. If you run a building or contracting business, generic bookkeeping advice will not cut it.

The construction industry operates on a project-by-project basis. You need to track costs per job, manage retention payments, handle progress claims, and juggle dozens of subcontractors - all while staying compliant with tax obligations.

Job Costing: The Heart of Construction Bookkeeping

Job costing is the practice of tracking every dollar spent on a specific project. It is the single most important bookkeeping concept for builders, and getting it right means the difference between profitable projects and ones that quietly drain your business.

What to Track Per Job

Every job should have its own cost centre or tracking category. Within each job, you need to capture:

Direct materials - Timber, concrete, steel, plumbing fittings, electrical components, and every other material that goes into the build. Record the actual cost, not the quoted amount. Track delivery charges separately so you can see your true material costs.

Labour costs - This includes wages for your employees and payments to subcontractors. Break labour down by trade where possible - knowing that your electrical costs blew out on a project is more useful than knowing "labour" was over budget.

Subcontractor costs - Track each subcontractor separately. Record their quote, any variations, and the actual amount paid. This helps you identify reliable subs and flag those who consistently come in over budget.

Equipment and plant - Whether you own or hire equipment, allocate the costs to the relevant job. If you own a excavator and use it across three jobs in a month, split the depreciation and running costs proportionally.

Overheads allocation - Some businesses allocate a percentage of overheads (office rent, insurance, vehicle costs) to each job. This gives a more accurate picture of true job profitability.

Setting Up Job Costing in Your Software

Most cloud accounting platforms support job costing through tracking categories or projects. In Xero, you can use tracking categories to tag every transaction with a job number. Tools like SortBooks can automatically categorise transactions and assign them to the correct job, saving hours of manual data entry each week.

Create a consistent naming convention for your jobs. Something like "2026-001 Smith Residence" makes it easy to sort and find projects. Keep the convention consistent and train every person who touches the books to use it.

Progress Claims and Revenue Recognition

Unlike a shop that sells a product and records the revenue immediately, construction businesses recognise revenue as work progresses. This creates complexity in your books.

How Progress Claims Work

A typical construction contract involves the builder submitting monthly progress claims to the client. The claim shows the percentage of work completed and the corresponding value. The client (or their quantity surveyor) reviews the claim, and once approved, payment follows.

In your books, you should:

1. Record the progress claim as an invoice when submitted
2. Track the approved amount versus the claimed amount
3. Record any variations separately
4. Monitor the retention amount withheld

Retention Accounting

Retention is a percentage (usually 5-10%) withheld from each progress payment as security for defects. The retention is typically released in two stages - half at practical completion and half at the end of the defects liability period.

You need a separate account in your chart of accounts for retention receivable. When you issue a progress claim for $100,000 with 5% retention, you record $95,000 as accounts receivable and $5,000 as retention receivable.

Subcontractor Management

Managing subcontractor payments is one of the biggest administrative burdens in construction. Here is what you need to stay on top of:

Verify ABNs - Before paying any subcontractor, verify their ABN is active and valid. If they do not provide a valid ABN, you are required to withhold 47% from their payment.

Taxable Payments Annual Report (TPAR) - If you pay subcontractors for building and construction services, you must lodge a TPAR with the ATO by 28 August each year. This report details every payment made to every subcontractor. Keep your records meticulous throughout the year to avoid a painful scramble in August.

Written agreements - Always have a written agreement with your subcontractors. It protects both parties and provides clarity for your bookkeeping.

GST Considerations for Builders

Construction has specific GST rules that trip up many builders:

Margin scheme - If you are a property developer, you may be able to use the margin scheme for GST on property sales. This can significantly reduce your GST liability.

Going concern - The sale of a commercial property as a going concern may be GST-free if specific conditions are met.

Progress payments - GST is generally payable when you receive a progress payment, not when you issue the claim. This timing difference matters for your BAS reporting.

Common Construction Bookkeeping Mistakes

Not tracking costs per job - Some builders lump all expenses together and only look at the overall profit. This hides unprofitable jobs and makes it impossible to quote accurately for future work.

Ignoring work in progress (WIP) - WIP represents the value of work you have completed but not yet billed. If your balance sheet does not include WIP, your financial position is understated.

Poor variation tracking - Variations are a major source of profit (or loss) on construction jobs. Track every variation, get written approval, and invoice promptly.

Mixing personal and business expenses - This is common across all industries but especially problematic in construction where the amounts are large. Use separate bank accounts and credit cards for business transactions.

Setting Up Your Construction Bookkeeping System

1. Choose the right software - Xero or QuickBooks with job costing capabilities are solid foundations. Add a tool like SortBooks to automate transaction categorisation and job allocation.

1. Create a detailed chart of accounts - Include separate accounts for materials, labour, subcontractors, equipment, and overheads. Add accounts for retention receivable and WIP.

1. Implement a job numbering system - Every project gets a unique number from day one. All transactions are tagged to this number.

1. Set up regular reconciliation - Reconcile your bank accounts weekly at a minimum. Construction businesses with high transaction volumes should consider daily reconciliation.

1. Review job profitability monthly - Run job profitability reports monthly and compare actual costs to your budget. Catch overruns early before they become unrecoverable.

Key Takeaways

Construction bookkeeping demands discipline and structure. Job costing is non-negotiable. Retention accounting needs its own workflow. Subcontractor management requires consistent processes. And GST compliance has industry-specific nuances you cannot afford to ignore.

The good news is that modern cloud accounting tools make all of this manageable. Set up the right systems from the start, stay consistent, and your books will give you the visibility you need to run profitable projects.