Most subcontractors do not go under because they took on bad jobs. They go under because cash showed up two weeks after payroll did.

A 13-week cash forecast is the financial tool that fixes that problem before it kills you. It is a rolling, weekly view of every dollar coming in and going out over the next 91 days. Treasury teams at large companies have run one for decades. Most subs do not, which is strange given that construction cash flow is arguably the lumpiest in the entire US economy: the industry average Days Sales Outstanding sits at roughly 90 days, according to the Rabbet 2024 Construction Payments Report and PwC data cited by Siteline, about double the 45-day threshold finance analysts consider healthy for commercial businesses.

This article walks through what a 13-week cash forecast is, why it matters more for subs than almost any other type of business, what goes in it, how to build one without a finance team, and the weekly rhythm that makes it actually work.

What a 13-week cash forecast actually is

Strip away the jargon: it is a spreadsheet, or software view, with 13 columns across the top, one per week for the next quarter, and a stack of rows showing every cash inflow and outflow you can reasonably predict. The bottom row is your projected ending bank balance for each week.

Three things make it different from a budget:

• It is weekly, not monthly. Cash crises happen on Friday morning, not in the quarterly review.
• It is rolling. Every week, you drop the week that just closed and add a new 13th week at the far end. The forecast is always 13 weeks out.
• It is cash, not accrual. It does not care what you billed. It cares what hit the bank.

The standard finance reference describes it as a tool that bridges the gap between daily cash management and the annual budget. For construction, that bridge is the whole point. Your WIP schedule tells you what you have earned. Your AR aging tells you what is outstanding. Neither tells you whether you can make payroll on the 15th.

Why subcontractors need this more than almost any other business

A regular business gets paid within 30 days of sending an invoice. A subcontractor does not.

The numbers are not subtle:

82 percent of contractors wait 30 or more days past the expected payment date, up from 49 percent just two years earlier.

72 percent of subcontractors specifically wait longer than 30 days for payment.

Only 5 percent of subcontractors report getting paid on time, per CCFG Credit 2024 data.

75 percent of subcontractors front material costs from their own cash reserves while waiting for the owner to pay the GC, who then pays the sub.

Mobilization Funding 2025 Construction Delays and Payment Timing Report found that one in four construction professionals named late payments as a major cause of project delays, and 66 percent said small construction businesses face more financial strain from late payments than large firms.

And that is before retainage. Retainage typically runs 5 to 10 percent of every progress payment and is held until the project reaches substantial completion or beyond, sometimes for years. California Senate Bill 61 caps private-project retention at 5 percent starting January 1, 2026, joining New York, which enacted a similar 5 percent cap in November 2023. Other states still allow 10 percent, and federal projects can withhold up to 10 percent under the FAR. The point: retainage rules vary by state, project type, and contract. Check yours, and talk to your attorney if it is material.

Here is what all of that means in plain English. You finish work in January. You bill on a G702 and G703 in early February. The GC pulls 10 percent retainage and sends the rest to the owner with their own pay app. The owner reviews. The lender funds. The GC eventually pays you in March or April. Your retainage sits in escrow until late summer at the earliest. Meanwhile your crew got paid every Friday from January through April, and your supplier wants their net-30 settled by Valentines Day.

That gap, between the moment work happens and the moment cash hits, is where subs die. A 13-week forecast is what makes the gap visible before the bank balance hits zero.

The five categories every subcontractor forecast needs

Most generic 13-week templates are built for SaaS companies and consultants. Throw those out. A construction-specific forecast has to handle these five categories:

1. Receivables, net of retainage

Not what you billed. What you will actually collect, when you will actually collect it.

For each open pay app, write down:

• Submission date
• Expected approval date, use the GC actual historical pattern, not the contract
• Expected wire or check date
• Net amount, billed amount minus retainage minus prior payments

If a GC has paid you 14 days late on average for the last six months, forecast 14 days late. Optimism is not a strategy.

2. Retainage releases

These are receivables, but they need their own row because they behave differently. Retainage does not move with progress billing. It moves with substantial completion, punch list closeout, lien releases, and sometimes pure inertia. Mark expected release dates conservatively, and only put retainage in the forecast when you have a documented reason to believe it is actually coming that week.

3. Labor, payroll, taxes, workers comp, benefits

Payroll is the most predictable outflow you have and the most dangerous one to miss. Forecast gross payroll plus payroll taxes plus workers comp accruals plus benefits, on the actual day they hit your account. If you pay weekly, that is 13 known outflows over the next 91 days. Do not smooth them. Hit them on the actual day.

4. Materials and supplier AP

Group these by supplier or by net terms. Some suppliers are net-30. Some are net-15. Some are COD on the next order if you are behind. Pull your AP aging and put each invoice in the week it is due, not the week you would like to pay it.

If you finance materials through a supplier credit line or a third-party financing product, separate the principal and any interest into their own lines. They have different timing.

5. Sub-subs, equipment, and overhead

Everything else: lower-tier subs you owe, equipment rental, fuel, insurance premiums, especially the big quarterly or annual hits, rent, software, owner draws, debt service. Put real dates next to each one. Overhead as a single lumped line is a forecast that lies to you.

How to build your first 13-week forecast, a practical walkthrough

You do not need a CFO to do this. You need about three hours the first time and 30 to 45 minutes per week after that.

Step 1: Open a spreadsheet with 14 columns.

Far left is the line item. Then 13 columns, one per week, with the week-ending date as the header.

Step 2: Put your current bank balance in the top-left of week 1.

That is your starting cash. Include operating accounts only. Exclude anything you would actually have to fight to access.

Step 3: Build the inflow rows.

Open AR by customer, with expected pay date and net-of-retainage amount. Add a separate row for retainage releases you genuinely expect this quarter. Add a row for any committed change orders that will bill in the next 90 days. Do not forecast inflows you hope will happen.

Step 4: Build the outflow rows.

Payroll by pay date. Payroll taxes by deposit schedule. AP by supplier and due date. Sub-sub draws. Equipment. Insurance premiums. Loan payments. Owner draws. Tax estimates. Anything that touches the bank.

Step 5: Calculate weekly net cash flow and running ending balance.

Each week: starting cash plus inflows minus outflows equals ending cash. Ending cash carries to next week starting cash. The story is in that bottom row.

Step 6: Stare at the bottom row.

Look for the week where the number turns red, gets close to your minimum operating cash threshold, or drops below what you need to cover the next two weeks of payroll. That is the week you have to act on now, not the week it happens.

Step 7: Build two scenarios.

Base case, your honest forecast. Downside case, every GC pays 15 days later than expected, one material order doubles, one retainage release slips a quarter. The downside case is the one that tells you how much credit headroom you actually need.

Here is a clearly hypothetical example to make the math concrete:

A drywall sub has 400,000 dollars in open AR across three jobs. Two GCs pay reliably at day 45. One GC has been stretching to day 70 lately. Retainage on the active jobs sits at 62,000 dollars, none of it scheduled for release in the next quarter. Weekly payroll runs 58,000 dollars burdened. Materials AP due in the next 30 days is 145,000 dollars.

A naive forecast says: 400,000 coming in, 145,000 going out for materials, 58,000 times 13 weeks for payroll equals 754,000 in obligations against 400,000 coming in.

A 13-week forecast says something more useful: of that 400,000, only 230,000 actually lands in weeks 1 through 6. The slow GC 170,000 will not hit until week 10. Materials AP clusters in weeks 2 and 4. Without action, the ending balance dips below the payroll-safe threshold in week 5, even though the books look profitable.

The action: accelerate billing on the next pay app cycle, push one supplier from net-15 to net-30, and confirm the line of credit can carry weeks 5 through 9. None of that is possible without seeing it on a single page.

Numbers are illustrative only, not industry averages.

The weekly rhythm that makes it stick

A 13-week forecast that gets built once and abandoned is worse than no forecast at all. It creates false confidence. The rhythm matters as much as the model.

A workable cadence:

• Monday morning, 20 minutes. Pull the current bank balance. Replace last week projected numbers with actuals. Note variances. Anything off by more than about 10 percent needs a quick why.
• Monday afternoon, 15 minutes. Look ahead two weeks. Anything that needs to be invoiced, escalated, collected, or paid early? Make the calls.
• Friday afternoon, 10 minutes. Confirm next week payroll funding. Flag any GC payment that should have hit this week and did not.

That is it. Forty-five minutes a week to stop running the business by gut feel.

Common mistakes subs make with cash forecasts

A few patterns that show up over and over:

• Forecasting what you will bill instead of what you will collect. Billing is not cash. Cash is cash. Forecast the cash.
• Treating retainage as a normal receivable. Retainage has its own calendar. Do not park it in the same row as 30-day AR, it will quietly inflate your projected balance.
• Ignoring quarterly hits. Workers comp audits, insurance premiums, tax estimates, and bonus payouts wreck more forecasts than slow GCs do. Put them in the model the day you know about them.
• Forecasting monthly because weekly feels like overkill. Construction outflows are weekly. A monthly forecast hides the exact week you go negative.
• Updating it whenever you get around to it. That is not a forecast. That is a screenshot from three weeks ago.
• No downside scenario. Base case only is for businesses that do not depend on other people payment behavior. You depend on other people payment behavior.

What this means for your business

A 13-week cash forecast does not make GCs pay faster. It does not release retainage. It does not change the FAR. What it does is move you from reacting to predicting, which is the difference between calling your banker three weeks ahead of a cash gap, when they can help, and calling them three days after one, when they cannot.

This is the financial reality Breva was built around. The work-to-cash cycle in construction is too long, too lumpy, and too invisible, and visibility is the first thing that has to change. Breva bookkeeping, AP and AR, and cash plan tools are designed to keep this kind of forecast current without a finance team, because the contractors who consistently see their cash 13 weeks out are the ones who consistently get to keep building.

If you are running a sub and you have never built a 13-week forecast, or you built one once, in a spreadsheet, in 2022, the first version does not have to be perfect. It has to exist. Open the sheet today. The discipline compounds.

Want a clearer view of what your billing cycle is actually doing to your cash?

Breva helps construction businesses see their pay apps, retainage, AP, payroll, and bank balance on one page, so the 13-week view is something you live in, not something you build from scratch every Friday.

Want a clearer view of what your billing cycle is doing to your cash? See how Breva works for contractors, or start a free Breva account and get your billing, job costs, and cash plan working from the same numbers. Prefer to talk it through? Book a meeting.

Win jobs. Get paid.

Frequently Asked Questions

What is a 13-week cash forecast?

A 13-week cash forecast is a rolling, weekly projection of every cash inflow and outflow over the next 91 days, with a running ending bank balance for each week. It is a treasury-team standard adapted for any business with lumpy cash flow, including most construction subs.

Why 13 weeks and not 4, 8, or 26?

Thirteen weeks equals one quarter. Long enough to see a cash gap forming and short enough to forecast with reasonable accuracy. Shorter horizons miss problems. Longer ones drift into guessing.

How is a 13-week forecast different from a WIP schedule?

A WIP schedule shows revenue earned versus billed. A 13-week forecast shows cash projected to hit the bank. Both matter. The WIP tells you whether the job is healthy. The forecast tells you whether the company is.

Do I need software for this?

You can start in a spreadsheet. The challenge is keeping it current as pay apps move, retainage slips, and AP turns over. Most subs eventually outgrow the spreadsheet, not because the model gets complicated, but because the upkeep gets exhausting.

How accurate should my forecast be?

A useful forecast is right within roughly 10 to 15 percent on the weekly ending balance for the first 4 weeks, and trending in the right direction for weeks 5 through 13. Perfect accuracy is not the point. Useful accuracy is.

Should I include retainage?

Yes, but on its own row, and only schedule a release in a specific week when you have a real reason to believe it will happen. Otherwise, leave it parked. Retainage release timing is a documented headache. Build the forecast around that reality.

How often should I update it?

Weekly. Monday is the natural day. Replace last week projections with actuals, then look forward.

This article is for informational and educational purposes only and does not constitute legal, accounting, tax, or financial advice. Retainage, prompt-payment, and lien laws vary by state, project type, and contract. Consult your attorney, CPA, or financial advisor before acting on the information in this article.