Banks lend to engineering firms against billed receivables, usually with a cash-flow test behind them. Lenders typically advance 80% to 90% of eligible invoices and exclude anything more than 90 days past invoice, which matters for firms with slow public clients. Unbilled work in progress and retainage rarely count, or count only under a small sublimit. The line is therefore sized off what the firm has invoiced, while its cash need is driven by what it has worked. Expect covenants on debt service coverage and net worth, and limits on distributions and on buying out owners.
- Borrowing base
- Billed receivables, typically 80% to 90% of eligible
- Usually excluded
- Unbilled work, retainage, invoices over 90 days
- Typical lender
- A bank, often with a receivables formula behind a cash-flow line
- Common covenants
- Debt service coverage, tangible net worth, limits on distributions
- Firm-specific risk
- Ownership transitions and the departure of key principals
- Document that decides it
- A project-level WIP schedule that ties to the AR aging
Where an engineering firm's cash goes
Nearly all of an engineering firm's cost is people. Engineers, designers, drafters and field technicians are paid every week or two. Subconsultants, such as surveyors, geotechnical specialists and building-systems designers, are paid under their own agreements, often only once the firm itself is paid. Reimbursable costs like laboratory testing, travel and printing go out as they are incurred.
Revenue follows a longer route. The firm does a month's work, then prepares an invoice, often with a progress report the client must approve. Public clients, such as transportation departments, municipalities and utility authorities, route the invoice through their own approval layers before paying. Private developers frequently pay when their own construction financing funds a draw. The result is a firm that has typically carried a month of payroll before it even sends the invoice, then waits again to be paid.
Two things make the gap swing. Field services, such as surveying, construction inspection and materials testing, follow the construction season, so payroll peaks in the months when collections are still catching up with the spring. And a large award often means hiring before the first invoice can go out. Both are what a line is for; a firm with a pronounced seasonal swing should read seasonal lines of credit.
Billed, unbilled and retained: what counts
An engineering firm's balance sheet usually shows more receivables than a lender will count. The gap is in three places: work not yet invoiced, amounts the client is holding back, and invoices that have aged out. The general rules are in eligible vs ineligible receivables; this is how they apply to a firm's ledger.
| Item | What it is | Typical treatment |
|---|---|---|
| Billed invoices within terms | Work invoiced and accepted, not yet paid | Eligible |
| Invoices more than 90 days past invoice | Common with public clients and disputed scope | Ineligible |
| Unbilled work in progress | Hours worked this month or last, not yet invoiced | Ineligible, or allowed under a small sublimit for firms that bill promptly |
| Retainage | A share of each invoice the client holds until the project is complete | Ineligible until it is released and billed |
| Pass-through subconsultant billings | The subconsultant's work, billed to the client by the firm | Eligible, but some lenders reserve for the subconsultant payable tied to it |
| Disputed invoices and unapproved change orders | Work the client has not agreed to pay for yet | Ineligible |
| All invoices of a client with too much past due | The cross-aging rule | Ineligible once that client's past-due share passes the lender's limit |
Where a lender does allow unbilled work, it usually does so under a sublimit at a lower advance and only for work billed within a short, defined window. For the cross-aging rule, see the glossary.
How contract type changes the risk
Lenders read an engineering firm's contract mix the way a bonding company reads a contractor's: by who bears the risk of a cost overrun and how quickly work turns into an invoice.
- Time and materials, and hourly contracts with a ceiling. Billed monthly for hours actually worked. The receivable is clean, and the lender's main question is whether the ceiling is close.
- Cost-plus-fixed-fee public contracts. Billed on audited overhead rates. Reliable, but slow to pay, and an overhead rate lowered after an audit can claw back amounts already billed and collected.
- Lump-sum design contracts. Billed on a percentage of completion or on milestones. Profitable when well estimated, but the firm carries the overrun, and billing can lag the work.
- On-call and task-order contracts. Many small assignments under a master agreement. Good diversification, but the aging fills with small invoices that are easy to lose track of.
Reading the WIP schedule
The single most useful document in an engineering firm's line application is a work-in-progress schedule: every open project, with its contract value, cost to date, estimated cost to complete, billed to date and the resulting over- or under-billing. A lender uses it to check that the receivables are real and that the firm is not quietly financing its clients.
In plain numbers: a lump-sum design contract is worth 1,000. The firm has spent 450 and estimates the job will cost 800 in all, so it is a little over half done and has earned about 563. It has billed 400. The difference, about 163, is under-billed: work done that the line cannot lend against. If the estimate to complete rises and the total cost becomes 900, the job is only half done, earned revenue drops to 500, and the profit the firm expected on the job falls from 200 to 100.
A lender reading a schedule full of under-billings asks one question: is the firm slow to invoice, or are its lump-sum jobs running over? The first is fixable with better billing discipline and usually lifts availability quickly. The second is a profitability problem the line cannot solve. Over-billings, where the firm has invoiced ahead of the work, are the reverse: they help cash today, but the lender treats them as work the firm still owes.
A WIP schedule that ties to the general ledger and the AR aging does more for an engineering firm's line than any other document it can provide.
Public clients and the 90-day line
Firms heavy in public work often have the strongest customers and the weakest borrowing base. The client will pay; it just takes a long time, and every invoice that drifts past 90 days drops out of availability. A firm that tracks its days sales outstanding by client can see the problem coming: an agency that reorganized its approval process, a project manager who is late with progress reports, a funding source waiting for a budget.
Two practical fixes help most. Invoice on the client's required form, with the backup the client needs, on the first submission, because a rejected invoice restarts the clock. And follow each invoice through approval rather than waiting for payment. Federal work adds one more step: before most lenders count a federal receivable, the firm assigns its right to payment under the government's assignment of claims procedure, explained in lines of credit for government contractors.
Covenants, ownership and what trips firms up
Bank lines to engineering firms usually carry a debt service coverage covenant, commonly at least 1.25x, and a balance sheet test such as minimum tangible net worth or a current ratio. Reporting is typically a monthly borrowing base certificate with the AR aging, quarterly financial statements and an annual CPA-prepared statement, reviewed or audited as the line grows. Many lines also cap distributions and payments to owners; see restricted payments.
Ownership is where engineering firms differ most from other borrowers. Many are owned by a group of principals who retire in turn and are bought out by the firm, often with a note paid over several years. Those redemption notes are debt: they count in the coverage test, and the lender usually requires them to be subordinated to the line under a subordination agreement. Firms that transfer ownership to employees through an ESOP take on a further layer of debt, covered in ESOP financing.
- Funding a buyout from the line. Paying a retiring principal out of the revolver turns working capital into permanent debt and usually breaks a covenant.
- Billing lag. A firm that invoices weeks after month-end has a smaller borrowing base than its work justifies.
- Hiring ahead of an award that slips. A delayed notice to proceed leaves new payroll with nothing to bill.
- A professional liability claim. Lenders ask about open claims and whether insurance covers them; an uninsured claim can change the credit.
- Departing principals. Clients often follow the engineer, not the firm. Lenders ask who holds the key relationships and whether non-solicitation terms protect them.
The documents a lender reads follow Transparent's line of credit checklist: an AR aging by client with days outstanding, the AP aging, the balance sheet, the P&L and a year-to-date P&L through last month-end, and a debt schedule showing existing liens and any redemption notes, plus bank statements and two to three years of business tax returns where available. For an engineering firm, add the WIP schedule and the backlog of signed work. Firms buying another practice should also read financing an engineering firm acquisition.
Common questions
- Will a lender count our unbilled work in progress?
- Usually not, or only under a small sublimit at a lower advance for firms that bill promptly and consistently. The practical answer is to invoice faster: work turns into borrowing base the day it is invoiced.
- Does retainage count toward the borrowing base?
- Not while the client is holding it. Retainage is released only when the project or phase is complete and accepted, so lenders treat it as ineligible until it is billed as a current invoice.
- Can we use the line to buy out a retiring principal?
- Lenders generally object. A buyout is a long-term payment and belongs on a term loan or a subordinated note, not on a revolving line meant to rise and fall with receivables.
- Our public clients pay slowly. How does that affect the line?
- Invoices more than 90 days past invoice typically drop out of the borrowing base, and a client with too much past due can have all its invoices excluded. Tracking approvals and submitting clean invoices the first time is the most effective fix.
- What do lenders make of a firm with many small owners?
- They look at the shareholder agreement: how owners are bought out, on what terms, and whether those payments are subordinated to the bank. A clear, funded succession plan reassures a lender more than a single dominant owner does.