Construction finance is hard because the money moves through a structure no other industry uses. A bill is a pay application against a schedule of values. Every payment has retainage withheld. Payment is gated by lien waivers. Subs are paid only after the GC is paid by the owner. And the whole chain runs on monthly cycles with receivables that stretch past 80 days. The result is that contractors, especially subcontractors, finance the projects they work on out of their own cash. This playbook lays out how the money actually flows and the levers that pull cash in faster.
Why is construction cash flow structurally hard?
The core problem is timing. Costs are incurred now, weekly payroll and material bought on 30-day terms, while revenue arrives months later and in pieces. A subcontractor mobilizes, buys material, and makes payroll for weeks before it can even bill, then waits through a monthly cycle, a GC review, and the GC's own wait on the owner, before any cash comes back. On top of that, retainage holds back a slice of every payment until closeout. Profit on paper and cash in the bank are two different things in construction, and the gap between them is financed by the contractor.
How does construction accounts payable work?
On the payable side, a construction invoice is rarely a flat bill. From subcontractors it arrives as a pay application, often AIA forms G702 and G703, claiming a percent complete against a schedule of values, with retainage and prior billings netted out. Approving it means reviewing each line against the work actually in place, checking the retainage math, matching to the commitment or purchase order, confirming the required lien waiver is in hand, and coding each line to a job and cost code. That last step matters because construction measures profit per project and per phase, so a miscoded invoice corrupts the job cost report a project manager runs the job by.
AP in construction is a document-understanding problem
Reading the header total off an invoice is the easy part. The work is extracting the schedule of values lines, applying retainage, matching to the commitment, and coding to the job. General AP tools stop at the header. Construction AP has to understand the pay application as a construction document.
How does retainage work, and where does it trap cash?
Retainage is a percentage of each progress payment withheld until the work is complete, meant to give the owner a hold on the money until the job gets finished. Private construction retainage averages around 7.59 percent according to a study by the Foundation of the American Subcontractors Association, and states cap it on public work, for example 5 percent in California. It sits on both sides of a general contractor's ledger: the GC withholds it from subs and has it withheld by the owner, with different release timing on each side. For a subcontractor, the retention held across a job often approaches the profit on that job, which means the entire profit can be locked up until closeout, released a year or more after the work was done.
What role do lien waivers play?
A lien waiver is a document by which a payee gives up mechanics lien rights for the amount being paid, and payment is usually conditioned on it. There are four types, formed by two choices: conditional or unconditional, and progress or final. A conditional waiver takes effect only when payment actually clears. An unconditional waiver is effective on signing, whether or not the money arrived. Signing an unconditional waiver before the check clears waives your lien rights for money you have not received, which is a real and avoidable exposure. Managing waivers means tracking which type is required, whether it was exchanged, and that it matches the payment, on both the paying and receiving side.
How does accounts receivable and DSO work in construction?
Days sales outstanding, or DSO, measures how long it takes to collect a receivable after billing, and construction runs one of the highest figures of any industry, commonly cited around 80 days and up in industry surveys, versus roughly 40 days in many other sectors. The drivers are structural: pay-when-paid clauses put the sub behind the GC, the GC waits on the owner, monthly billing adds weeks, and retainage stretches the tail past a year. DSO is calculated as accounts receivable divided by credit sales, times the days in the period. The number is most useful tracked by customer, because one slow GC can drag the whole figure and mask that the rest of the book pays on time.
A worked example of the cash gap
Follow a single subcontract. The sub buys material and pays in 30 days. It runs payroll weekly for the months crews are on site. It bills monthly, then waits two to four weeks for the GC to review the pay application, and the GC pays only after the owner pays the GC. Retainage is withheld from every payment. So the sub has funded weeks of payroll and material before the first dollar arrives, and the last dollar, the retention, lands a year after the work is finished. Nothing in that sequence depends on the job being unprofitable. It is the structure.
What is pay-when-paid versus pay-if-paid?
These two clauses decide who carries the risk when an owner does not pay, and the difference is enormous for a subcontractor. A pay-when-paid clause is generally read as a timing provision: the GC can wait a reasonable time to pay the sub while it pursues the owner, but it still owes the sub eventually. A pay-if-paid clause tries to make the owner's payment a true condition of the sub ever being paid at all, shifting the risk of owner nonpayment onto the sub. Many states limit or refuse to enforce pay-if-paid clauses because of how harsh that shift is, but where they hold, a sub can do everything right and still not get paid because someone upstream did not. Reading which clause is in your subcontract, before you sign, is a cash-flow decision as much as a legal one.
The practical response is to know your contract terms, preserve your lien and bond rights so you have a claim that does not depend on the clause, and price the risk of a slow or shaky owner into the job. A subcontractor cannot always negotiate the clause away, but it can refuse to be surprised by it, and it can make sure that if the money is slow it still has the mechanics lien or payment bond claim that gets it to the front of the line.
How do you pull cash in faster?
- Bill on time and bill clean, because a pay application with a math error or a missing lien waiver gets kicked back and restarts the whole monthly cycle.
- Send the conditional lien waiver with the billing, not after, so a missing waiver is never the reason a payment is held.
- Track retention per job and per customer, and request release the day a job closes out instead of finding it months later.
- Measure DSO by customer, so you know which GCs actually cost you money to work for and can price or prioritize accordingly.
- Work aged receivables on a schedule, because the invoice that gets a call gets paid ahead of the one that does not.
- Code payables to the right job and cost code, so the job cost report is accurate enough to catch a losing job while there is still time.
The theme across the payable and receivable sides is the same: construction finance is an operational discipline, not a byproduct of good clients. Buildalytic reads pay applications and invoices, tracks retainage and lien waivers on both sides, measures receivables and DSO by customer, and writes back to the system of record you already run, so the cash that has been earned actually comes in rather than sitting in a receivable no one is chasing.