Cashflow management for residential builders

TL;DR

A residential builder’s cashflow has a few large inflows (deposits, stage payments) and many smaller outflows (trade invoices, materials, payroll, BAS). The gap between them is what kills small builders. Three operational disciplines close most of the gap: bill the next stage the day the previous stage signs off, hold a 5-10% working capital buffer per active job, and treat BAS and PAYG payroll as untouchable liabilities, not “today’s cash”. Most cashflow incidents in residential building come from blurring those three lines, not from external shocks.

The shape of builder cashflow

A 6-month, $600,000 fixed-price residential build typically pays:

Stage	% of contract	Indicative cash	Timing
Deposit	5%	$30,000	Contract signing
Base (slab + footings)	15%	$90,000	Week 2-3
Frame	20%	$120,000	Week 6-8
Lockup	20%	$120,000	Week 12-14
Fixing	25%	$150,000	Week 18-20
Practical completion	15%	$90,000	Week 24
Retention release (some contracts)	0-2%	$0-$12,000	Defects period end (3-6 months)

Outflows over the same 6 months: trade invoices ($350,000-$450,000), materials direct from builder accounts ($50,000-$120,000), labour/PAYG payroll ($50,000-$100,000), site costs ($20,000-$40,000), GST ($30,000-$50,000), plus the builder’s own draw.

The danger zones are the gaps between stages and the lockup-to-fixing valley.

Stage-gap discipline

A standard stage gap is the period between completing a stage and receiving the stage payment. On a well-run residential build, this is 5-10 business days; on a poorly run one, it can be 4-6 weeks.

Closing the gap:

Pre-stage notification: tell the client 5 working days before the stage will complete so they can arrange the bank-draw. Banks need lead time.
Day-of-completion invoice: issue the payment claim the day the certifier signs off, not the next week.
Reference-date contracts (SOPA): claims align with the contract’s reference date. Issuing a claim on the wrong date can be defective; pick a reference date that suits the project program at contract negotiation.
Stage sign-off documentation: attach the certifier’s sign-off, photos, and an item-by-item completion confirmation. Clients pay faster when there’s clear evidence the stage is done.

A 3-week gap on a $120,000 frame payment costs the builder around $750 in finance cost (at typical overdraft rates) plus the operational stress of bridging trade invoices in the gap.

Trade and supplier payment terms

Most trade contracts in residential building are 14-day net from invoice, occasionally 30 days, occasionally pay-when-paid (Vic, NSW prohibit unreasonable pay-when-paid clauses but they still appear). Supplier accounts (timber yard, hardware, fixings) are typically 30-day net end-of-month (i.e. invoices through October are due 30 November).

The gap that opens:

Trade invoices land continuously through a stage.
Stage payment lands once at end of the stage.

If a frame takes 6 weeks and the chippy invoices monthly, the builder owes the chippy at week 4 for work done in weeks 1-4, before the frame payment lands at week 6+.

Bridging this on every stage requires a working capital buffer, typically 5-10% of the active contract value per job. On a $600k job, that’s $30,000-$60,000 of working capital sitting available.

BAS, GST, and PAYG: untouchable

The single most common cause of builder insolvency in Australia is using BAS-collected GST or PAYG-withheld wages as operating cash.

GST collected on a $120,000 frame stage payment is roughly $10,909 (1/11th of GST-inclusive). That money belongs to the ATO and is due quarterly. Treating it as today’s cash works for one quarter, but the bill arrives in three months and the builder is now structurally short.

Same logic for PAYG withheld from employee wages: that’s the employee’s tax, held in trust for the ATO.

The discipline: a separate “tax” account that gets the GST + PAYG portion of each stage payment swept immediately on receipt. Some builders use a high-interest savings account that rebates the float.

Quarter	Indicative BAS liability (residential builder, $1.5M annual turnover)
Q1 (Sep BAS)	$30,000-$50,000
Q2 (Dec BAS)	$30,000-$50,000
Q3 (Mar BAS)	$30,000-$50,000
Q4 (Jun BAS)	$30,000-$50,000

Missing a BAS payment triggers an ATO penalty interest charge (currently 11.36% p.a. compound) and General Interest Charge accruals. The ATO has wide enforcement powers, including DPN (Director Penalty Notice) personal liability for company directors.

Lockup-to-fixing valley

The lockup-to-fixing transition is the cashflow squeeze of most residential builds.

Why: at lockup, sheeting, roof, windows, and external doors are done. The lockup payment ($100,000-$150,000 typical) lands. But fixing stage (lining, painting, tiling, joinery, fit-off, kitchen) is the most trade-intensive period of the build. Trade invoices peak in fixing stage. The next stage payment (practical completion) is 6-10 weeks away.

Builders short of working capital can stall at fixing because they cannot keep paying tilers, painters, and joiners while waiting for PC.

The fix is to have between lockup and PC enough cash on hand to fund 6-10 weeks of fixing-stage trade invoices PLUS BAS PLUS payroll, without leaning on the PC payment. That’s the working capital buffer plus stage timing.

Retention and defects liability

Many residential contracts (and most state HBI / HBA schemes) have a defects liability period of 3-6 months and may withhold retention of 2-5% until the end. On a $600k build, that’s $12,000-$30,000 held back.

Retention is not cashflow until released; it’s working capital trapped. Budgeting needs to assume retention is paid 3-6 months after PC, not at PC.

Tools and disciplines

Discipline	What it looks like
13-week cashflow forecast	Updated weekly. Inflows by date, outflows by date, running bank balance
Job costing in Xero or Buildxact	Every invoice coded to a job; report shows job-level profit and remaining budget
Tax account	Separate ATO-money savings account, swept on stage payments
Working capital buffer	5-10% of active contract value across jobs
Reference-date discipline	Contract reference date set to suit the program; payment claims issued on schedule
Pre-stage client notification	5 working days before each stage triggers the bank draw

The most common builder mistake on a single build is missing one or two of these. The most common mistake across a portfolio is running multiple jobs without consolidating the cashflow forecast.

For builders

Pick a reference date pattern that matches the build program. Discuss with the client at contract.
Open a separate “tax” account if you don’t have one. Sweep 1/11 of every stage payment to it the day it lands, plus PAYG withheld.
Build a 13-week rolling forecast in a spreadsheet or accounting software. Update weekly. The day you see a week with negative bank balance is the day to act, not the day it lands.
Hold a working capital buffer sized to 5-10% of active contract value. Resist the temptation to fund the next job out of this.
Notify the client 5 days before each stage signs off. Banks need lead time; clients need to plan.

References

ATO BAS and GST: https://www.ato.gov.au/Business/GST/ (verified 2026-05-15).
ATO Director Penalty Notice: https://www.ato.gov.au/Business/Your-business-and-the-law/Director-penalty-notices/ (verified 2026-05-15).
Australian Taxation Office