Line-of-Credit Borrowing Base: How Receivables Set Your Available Cash

A $1 million line of credit does not mean the business can draw $1 million.

On an asset-based or borrowing-base line, availability usually depends on eligible collateral—often billed accounts receivable—after the lender applies advance rates, exclusions, concentration limits, and reserves. The outstanding balance, letters of credit, and other deductions reduce what remains.

For a service business, the borrowing base can shrink at the same time cash is under pressure. Receivables age, one customer becomes too concentrated, credits increase, unbilled work grows, or collections pay down the line through a controlled account. The facility amount printed on the first page is only the outer limit.

Start with the availability formula

A simplified receivables formula is:

Eligible accounts receivable
× Accounts-receivable advance rate
– Lender reserves
= Borrowing base

Lesser of borrowing base or facility commitment
– Outstanding loans
– Letters of credit and other agreement deductions
= Excess availability

Every term is agreement-specific. The lender may have discretion to change reserves or eligibility within defined standards. Use the signed credit agreement and most recent borrowing-base certificate.

Work through a service-company example

Assume the accounts-receivable aging totals $1,500,000. The agreement excludes:

• $140,000 more than the permitted age.
• $90,000 of unbilled or progress-billing amounts.
• $110,000 above a customer concentration cap.
• $45,000 of related-party, disputed, or credit-balance accounts.
• $15,000 of other ineligible receivables.

Eligible receivables are $1,100,000. At an 80% advance rate:

$1,100,000 × 80% = $880,000

The lender has established a $60,000 reserve, so the borrowing base is $820,000. The total facility commitment is $1 million, outstanding draws are $570,000, and a letter of credit uses $50,000.

Lesser of $820,000 base or $1,000,000 commitment  $820,000
– Outstanding line balance                         570,000
– Letter of credit                                  50,000
= Excess availability                              $200,000

The company has $200,000 available—not the $430,000 difference between the headline commitment and current draw.

Understand eligible receivables

Eligibility is a credit decision about expected collection and lender control. Common exclusions may include:

• Invoices older than a stated number of days from invoice or due date.
• Unbilled revenue and contract assets.
• Progress billings or invoices dependent on future performance.
• Disputed, offset, contingent, or credit-balance accounts.
• Related-party and intercompany receivables.
• Foreign receivables without approved support.
• Government, healthcare, or other specialized receivables unless permitted.
• Customer deposits, retainage, or self-pay balances under some structures.
• Receivables subject to liens, assignment restrictions, or inadequate documentation.
• Amounts above customer concentration limits.

An invoice being valid under the accounting policy does not make it eligible collateral. The lender applies the contract definition and may require evidence that the service was completed, accepted, billed correctly, and free of offsets.

The unbilled-revenue process should remain separate. Earned but unbilled work can support accounting revenue while contributing nothing to borrowing availability.

Apply aging and cross-aging rules

An individual old invoice may be excluded once it passes the agreement threshold. Cross-aging can exclude all receivables from a customer when too much of that customer's balance is past due.

Example: a customer owes $200,000. If $60,000 is beyond the specified age and the cross-age trigger is 25%, the entire $200,000 may become ineligible—not only the $60,000.

Monitor eligibility aging, not just the standard collections aging. The agreement may measure from invoice date while the A/R report emphasizes due date. A net-60 invoice can therefore consume much of a 90-day-from-invoice eligibility window before it is technically overdue.

Model customer concentration

A concentration limit prevents one account debtor from supporting too much of the base.

If eligible receivables before concentration are $1 million and the agreement caps one customer at 20%, only $200,000 from that customer may count. If the customer owes $350,000, the excess $150,000 is ineligible even when every invoice is current.

The effect can move unexpectedly. When other customers pay, the denominator shrinks and the concentrated customer's excess can grow. A large collection can reduce total receivables and line debt while also making the remaining base more concentrated.

Forecast the concentration calculation by customer through expected billing and collection dates. Do not wait for month-end.

Before committing more cash or adding another fix, book a free 20-minute Profit & Tax Leak Check to see which part of the financial model is creating the biggest leak.

Track dilution and reserves

Dilution is the reduction of receivables for reasons other than cash collection, such as:

• Credits and refunds.
• Billing errors.
• Discounts and allowances.
• Returns or service concessions.
• Write-offs and offsets.
• Rebilling or invoice cancellation.

Higher dilution can reduce the advance rate or create a separate reserve. Other reserves may address taxes, payroll, customer disputes, lien risk, chargebacks, appraisal findings, or other lender-defined exposures.

Tie credit memos to root causes. Persistent dilution is not only a financing problem; it may show weak scope, service quality, contract setup, or billing control.

Reconcile the certificate to the ledger

For every certificate:

1. Tie gross receivables to the closed general ledger.
2. Tie customer and invoice detail to the aging report.
3. Remove cash collected through the certificate date as required.
4. Apply each eligibility rule separately.
5. Calculate concentration and cross-aging in the specified order.
6. Apply advance rates and reserves.
7. Reconcile outstanding loans, letters of credit, and deductions to lender records.
8. Retain support and approval for the submitted certificate.

Do not alter invoice dates, delay credits, or leave collected invoices in the base. An inaccurate certificate can create an overadvance, default, and credibility problem.

The SBA's current lender materials for its 7(a) Working Capital Pilot emphasize timely financial statements, receivable and payable agings, and monitoring controls that mirror asset-based facilities. Even outside that program, those records are foundational.

Forecast availability weekly

Build the borrowing base beside the thirteen-week cash-flow forecast.

For each week, forecast:

• New eligible invoices.
• Cash collections and mandatory line paydowns.
• Receivables crossing an age threshold.
• Concentration movement.
• Expected credits and dilution.
• Reserve changes already communicated or reasonably expected.
• Planned draws, repayments, and letters of credit.
• The facility commitment and maturity.

Keep three numbers visible:

Gross borrowing base
– Debt and agreement deductions
= Excess availability

Excess availability
– Minimum availability or covenant requirement
= Usable availability above the required cushion

A company may technically have $200,000 of excess availability but only $125,000 above a required $75,000 minimum. Using the whole amount could create a covenant or cash-control problem.

Stress the borrowing base

Model named risks:

• Largest customer pays and the remaining base becomes concentrated.
• A disputed customer balance becomes ineligible.
• Collections delay until invoices cross the aging limit.
• Credit memos increase dilution.
• Unbilled work grows while eligible billing stalls.
• The lender adds a reserve after field examination.
• A covenant breach or reporting delay restricts advances.
• The facility reaches maturity before refinancing closes.

The purpose is not to predict lender discretion. It is to identify how much availability depends on facts the company can monitor and control.

Separate liquidity from revenue and profit

Recognizing revenue does not create eligible receivables. Issuing an invoice does not guarantee eligibility. Eligibility does not guarantee a draw, and a draw is borrowed cash—not operating cash generation.

Compare borrowing-base trends with operating cash-flow margin. If line usage rises while operating conversion remains weak, determine whether the facility is funding a temporary working-capital cycle or a structural cash deficit.

The cash-reserve model should count only unrestricted cash as reserve and show available line capacity separately. Borrowing availability can contract during the same stress that makes liquidity necessary.

Assign clear ownership

Process	Primary owner	Control
Contract and billing evidence	Operations and billing	Accurate, supported, timely invoices
Receivable aging and credits	Controller and A/R	Ledger reconciliation and reason-coded exceptions
Borrowing-base certificate	Controller with CFO review	Agreement rules, support, approval, timely submission
Availability forecast	CFO and treasury	Weekly billing, collection, eligibility, debt, and cash view
Agreement interpretation	Counsel and lender	Written confirmation for ambiguous terms

Do not make the A/R clerk solely responsible for interpreting a credit agreement. Do not let finance forecast draws without operating input on billing and customer disputes.

Use availability as a decision boundary

Before adding payroll, equipment, distributions, or another major commitment, ask:

• What is usable availability after the required cushion?
• Which customers and invoices support it?
• What happens after expected collections pay down the line?
• Which invoices age out before new billing enters?
• Does downside availability stay positive through payroll, tax, and debt dates?
• When does the facility renew or mature?

A borrowing base is a moving collateral formula. Managed well, it provides controlled working-capital capacity. Managed from the headline commitment, it creates surprise.

Sources

• Federal Deposit Insurance Corporation: Commercial and Industrial Lending
• U.S. Small Business Administration: SBA Lenders and 7(a) Working Capital Pilot
• U.S. Securities and Exchange Commission filing: receivables borrowing-base and eligibility example
• U.S. Securities and Exchange Commission filing: advance rate, dilution, and reserve example

Fractional CFO support can connect receivable quality, certificate controls, weekly availability, lender reporting, and cash decisions. The Profit & Tax Leak Check can identify whether billing delays, aged receivables, concentration, dilution, line terms, or structural cash use is reducing real availability.