What Is a Borrowing Base Certificate? The Formula Lenders Use to Decide What You Can Draw

Your credit facility might say $2 million. Your borrowing base certificate might say $1.1 million is available today.

That gap catches new asset-based borrowers off guard every time. The borrowing base is the actual math your lender runs against your receivables and inventory. It decides what you can draw, not the number printed on your term sheet.

For the short definition, see our glossary entry on borrowing base. This article is the full walkthrough: the formula, a worked example, and a calculator.

The formula itself has four moving parts. Lenders multiply eligible receivables by an AR advance rate. They multiply eligible inventory by a separate inventory rate.

Then they subtract reserves for risk. Not every dollar of AR or inventory counts toward that total.

This page covers the national mechanic: the formula, the terminology, and the math itself. See our Utah manufacturer borrowing base guide for the applied, calculator version.

Lenders don't hand you the entire limit on day one. They rerun this formula every reporting period, and the number moves with your collateral.

This distinction matters most for inventory-heavy or receivables-heavy businesses. A standard unsecured line of credit doesn't work this way at all.

See our collateral guide for how secured and unsecured lines compare more broadly.

The Borrowing Base Formula, Step by Step

Borrowing base equals eligible AR times the AR advance rate. Add eligible inventory times the inventory advance rate. Then subtract reserves.

Run real numbers through it and the mechanic gets clear fast.

Here's a full worked example, line by line.

These numbers aren't picked at random. Both rates fall inside the ranges the OCC's Comptroller's Handbook publishes. So the math mirrors what a real facility might return.

Plug the same five numbers into the calculator above. It returns the identical $525,000 net borrowing base.

That $525,000 is your actual draw availability, not the $550,000 gross figure.

Sometimes the borrowing base comes in lower than the facility limit suggests. Read on if the borrowing base doesn't cover what you were hoping to draw.

Why AR and Inventory Get Different Advance Rates

Receivables convert to cash in one step: the customer pays the invoice. Inventory needs two steps: it has to sell, then the sale has to collect.

More steps mean more risk. That's why AR usually gets the higher advance rate of the two.

Lenders also price off liquidation value, not retail value. What could a lender recover if it had to seize and sell the collateral fast?

Finished goods sold at a fire-sale price recover less than their sticker price. Raw materials recover even less, since they're one more step removed from a sale.

That's the real logic behind every advance rate in this article. Distance from cash, and certainty of recovery, drive the number down.

What Makes Receivables 'Eligible' vs. 'Ineligible'

Eligible receivables are invoices your lender will actually count. Ineligible receivables get carved out before any advance rate applies.

For the formal definition, see our glossary entry on eligible receivables.

• Receivables past due more than three times normal trade terms, commonly 90 days on 30-day terms
• Concentration beyond a lender-set cap, typically 10%–20% of the AR borrowing base for a single customer
• Affiliate or related-party receivables
• Foreign or government receivables without additional credit support, such as insurance or a letter of credit

Each of these exists to protect the lender against collection risk. A single large customer going bankrupt shouldn't collapse your entire facility.

Concentration caps surprise growing companies the most. Lenders flag a customer as "concentrated" at 10%+ of total AR. That threshold comes from the OCC Comptroller's Handbook.

Land one big account, and a large share of AR can age out of eligibility. That happens even when every invoice is current and collectible.

Dilution is a related but different problem. Customer disputes, returns, and early-pay discounts all reduce what an invoice actually collects.

Dilution typically runs 5% or less of receivables (OCC Comptroller's Handbook). Lenders track your dilution rate over time.

A rise above that norm often triggers a bigger reserve. That lowers your net borrowing base, even if gross AR looks fine.

What Makes Inventory 'Eligible' vs. 'Ineligible'

Eligible inventory usually means finished goods ready to sell. Raw materials and work-in-progress get discounted or excluded outright.

Finished goods commonly carry the full inventory advance rate. Raw materials and WIP often get a lower rate, or nothing at all.

Obsolete or slow-moving inventory is a common exclusion too. So is consigned inventory, since your business doesn't actually own it.

Valuation method matters too. Lenders advance against cost, not retail price. Larger facilities often require a professional appraisal to confirm it.

An orderly liquidation appraisal estimates what inventory would fetch in a controlled sale. That figure, not your catalog price, sets the eligible base.

Seasonal businesses feel this hardest. Seasonal inventory swings change the borrowing base month to month, sometimes by a wide margin.

That's why seasonal inventory financing gets structured differently from a standard revolving line.

How to Increase Your Borrowing Base

None of these fixes happen overnight. Each one moves the borrowing base in a real, measurable way.

Clean AR aging is the fastest lever. Collect or write off invoices before they age past 90 days.

Diversify your customer base where you can. A single account creeping past the concentration cap shrinks your eligible pool. That happens even as revenue grows.

Keep inventory records current. An outdated count understates what you actually have on the floor. Lenders can only advance against what's verified.

Move inventory toward finished goods faster. Every day spent as raw material or work-in-progress sits at a lower advance rate. Some categories get no advance rate at all.

Negotiate advance rates at renewal, not mid-term. Lenders revisit rates when your collateral quality and payment history have measurably improved.

Ask what's driving your reserves. A dilution reserve tied to a specific customer dispute may shrink once that dispute resolves. It's worth asking your lender directly.

How Often the Borrowing Base Is Recalculated

Monthly borrowing base certificates are standard for active asset-based facilities. Some lenders require weekly submissions during a field exam cycle.

Each certificate resets the eligible AR and inventory pools. Reserves and dilution adjustments get reapplied every time.

Lenders often check your DSCR at the same time. Collateral coverage and cash flow coverage answer two different questions.

Someone at your company, usually a controller or CFO, signs each certificate. Overstating eligible collateral on a certificate is a serious problem.

It can trigger a default under the credit agreement, even if the overstatement was accidental. Lenders take certificate accuracy seriously because they're relying on it to manage their own risk.

A well-run finance team treats the certificate as a discipline, not paperwork. That habit alone can prevent covenant surprises.

Field exams and ongoing monitoring aren't free. Lenders typically charge a commitment fee on the full facility. A separate monitoring fee often applies too, on top of interest on what you draw.

The exact blend varies by lender and facility size. It also depends on how much field-exam work your collateral requires.

On larger facilities, this cost scales with the size of the line. It's not just tied to the balance you've drawn.

Sometimes your outstanding balance briefly exceeds the borrowing base. Lenders call that an over-advance.

Most cap over-advances at 10% of the borrowing base (OCC Comptroller's Handbook). Frequent or long-running over-advances are a red flag lenders watch closely.

See how field exam and monitoring fees tie into the fee structure.

Frequently Asked Questions

Methodology: How We Built This Explainer

The advance rate, concentration, dilution, and over-advance figures here come from one named, checkable source. It's the OCC's Comptroller's Handbook, "Accounts Receivable and Inventory Financing" (booklet A-AR).

That's the federal bank examiner guidance used to evaluate this exact type of lending.

Per that handbook, AR advance rates commonly run 70%–80%. Inventory advance rates commonly run 20%–65%, with finished goods at the high end.

Field exam and monitoring costs are real, but the specific fee blend isn't publicly standardized. We don't quote a number we can't attribute to a named source.

We didn't rely on single-lender marketing claims for the collateral figures in this guide.

Your own facility's rates, caps, and reserves will differ. Confirm current terms directly with your lender before relying on any figure here.

Run the calculator above with your own numbers before your next draw request. The formula doesn't change. Only your collateral does.