What Is a Borrowing Base? The Complete Manufacturer's Guide

Your committed facility size is not your availability. That's the first thing most manufacturers learn the hard way after signing an asset-based lending agreement. A $10 million revolving line does not mean you can draw $10 million on day one. What you can draw is whatever your borrowing base says you can draw — and those two numbers are rarely the same.

The borrowing base is a real-time calculation. It rises when you ship product and generate receivables. It falls when customers pay and your AR balance drops, when inventory ages out of eligible status or when appraisals on your equipment decline. It moves with your business, not with the calendar. That's what makes it the central mechanic of any ABL deal.

Think of the committed facility as the maximum ceiling and the borrowing base as the actual ceiling on any given day. The lower of the two controls your draw. If your committed line is $10 million but your borrowing base calculates to $6.4 million, you can only access $6.4 million — even if your lender agreed in writing to $10 million.

For manufacturers running seasonal production cycles, building inventory ahead of peak demand or carrying receivables with 45-60 day payment terms, this mechanic matters enormously. A well-structured borrowing base can free up significant liquidity. A poorly negotiated one can leave capital stranded in assets the lender won't count.

The formula itself is straightforward. It's the application of advance rates to each eligible asset class, summed together:

Each variable in that formula has a specific definition that the lender controls. "Eligible" is the operative word — it's not simply all of your AR or all of your inventory. It's the portion the lender has agreed to count after applying their eligibility criteria. The advance rate then discounts that eligible pool to give the lender a cushion in case of default.

Typical Advance Rates by Asset Class

AR gets the highest advance rate because it's the most liquid and verifiable asset class. An invoice is a documented obligation from a real customer — it has a known face value, a payment date and a paper trail. Inventory gets less because liquidating it takes time, and equipment even less because it requires specialized buyers. The rates also reflect lender experience with recovery in defaults across each category.

Some facilities include a real estate component, typically advanced at 50-65% of appraised value. Others include intellectual property or specific contract rights, though these are far less common in manufacturing ABL deals and require specialized underwriting. For most mid-market manufacturers, the three-asset formula above is what you're negotiating.

For a deeper look at how these rates are set, see our advance rate guide for manufacturers.

Here's how the numbers play out for a mid-size metals fabricator with a $12 million committed ABL facility. The company has $8.2 million in gross AR, $4.1 million in finished goods inventory and manufacturing equipment appraised at $3.5 million orderly liquidation value.

The $1.1 million ineligible AR in this example comes from two invoices past 90 days, one government contract the lender excluded and one customer who hit the concentration limit. That's $1.1 million in receivables that look real on the balance sheet but produce zero borrowing base credit. Getting those resolved — faster collections, customer diversification — is how you push availability higher without changing the facility terms.

The $600,000 inventory haircut reflects a portion of raw materials the lender classified as slow-moving. Lenders often apply a separate NOLV (net orderly liquidation value) appraisal to inventory and use that appraised figure rather than book value as the starting point before applying the advance rate.

Lenders don't exclude receivables arbitrarily. Each ineligibility rule reflects a specific recovery risk. Knowing these rules before you negotiate lets you push back on the ones that don't apply to your customer base and accept the ones that do.

Age-Based Ineligibility

The standard cutoff is 90 days from invoice date. Some lenders use 60 days past due instead — which is a meaningful difference for companies with net-60 payment terms. If your invoice terms are net-30 and a customer pays at day 88, you're fine. But if your terms are net-60 and you use the 60-days-past-due trigger, that same invoice goes ineligible at day 120. Negotiate which trigger applies to your specific customer terms.

Cross-aging is the adjacent rule that catches many borrowers off guard. If more than 50% of a single debtor's total outstanding balance is past due (by whatever the defined threshold is), the entire balance from that debtor becomes ineligible — not just the past-due portion. One slow invoice from a large customer can wipe out an otherwise clean receivable pool.

Concentration Limits

Most lenders set a single-debtor concentration limit of 25% of total eligible AR. Any receivables from a debtor that push their share above that threshold are ineligible. For manufacturers with one or two dominant customers, this is often the most painful exclusion. The fix is customer diversification — which is easier said than done but is genuinely the correct answer from a credit risk perspective too.

Some lenders will raise the concentration limit for investment-grade customers — Fortune 500 companies, publicly traded entities — because the recovery certainty is much higher. Worth asking about if your largest customer is a blue-chip account.

Other Common Exclusions

• Government receivables (federal, state or municipal) — require specific UCC filings and assignment approvals that most ABL lenders avoid
• Foreign receivables — unless covered by credit insurance or a foreign receivables sublimit
• Contra accounts — if the debtor also owes money to your company, the receivable may be netted down
• Disputed invoices — any invoice under a formal dispute is typically excluded until resolved
• Related-party receivables — transactions between affiliated entities don't count

For a real-world look at how these exclusions affect a facility in practice, see our piece on ABL borrowing base mechanics.

The borrowing base certificate (BBC) is the document you submit to your lender — usually monthly, sometimes weekly — that reports your current eligible asset pools and calculates your available credit. It's a sworn certification. You're representing that the numbers are accurate. False certification is an event of default and potentially fraud.

Most lenders provide a template. The format varies, but the content is consistent: AR aging by debtor, inventory by category, equipment valuations by appraisal reference, ineligible amounts broken out by exclusion reason and the resulting borrowing base calculation. Your CFO or controller typically owns this process.

The AR aging schedule is the backbone. It has to reconcile to your general ledger. Lenders will audit the AR periodically — often quarterly for smaller facilities, monthly for larger ones. They're looking for invoices that don't correspond to actual shipments, customers who appear on the aging but haven't been verified and any pattern that suggests the aging is being manipulated to inflate availability.

What Triggers More Frequent Reporting

Most facilities start at monthly reporting. But certain conditions push lenders to require weekly or even daily BBCs. Watch for these triggers in your credit agreement:

• Availability falling below a specified floor (often $1-2 million or 10-15% of committed line)
• A covenant breach, even if waived
• A material adverse change determination by the lender
• An overadvance condition
• Audit findings that the lender deems material

Weekly reporting is manageable but adds operational burden. Daily reporting is genuinely disruptive. Structuring your facility to avoid the triggers that require it is worth prioritizing during negotiation. The Capital Access page covers how to approach these negotiations with lenders.

A revolving ABL facility is supposed to flex with your working capital cycle. That's the structural advantage over a term loan. The borrowing base is the mechanism that makes this work — but it also means your liquidity position changes month to month in ways that can surprise operators who aren't tracking it closely.

A manufacturer building inventory for a Q4 production run will see the borrowing base expand as eligible inventory accumulates. Then as they ship and convert inventory to AR, the inventory component drops and the AR component rises. As customers pay, AR drops and cash increases. The facility balance should move in sync with this cycle — drawn up during the build phase, paid down during the collection phase.

The danger period is the gap between when inventory becomes ineligible (because it's aged or partially obsolete) and when the AR from selling it is collected. Lenders won't advance against work-in-process inventory at the same rate as finished goods. Raw materials get the lowest rate. Finished goods get the highest. A manufacturer stuck in the middle of a production run may find their borrowing base compressed exactly when they need cash most.

Plan your facility draws against your actual cash conversion cycle, not your gut sense of how tight things are. Map the BBC calculation to your production schedule. See our discussion of asset-based lending for reshoring manufacturers for more on matching facility structure to production cycles.