What is the difference between an amortizing loan and an interest-only loan for a business?

How Amortizing Loans Work

An amortizing loan has a fixed repayment schedule where each periodic payment (monthly, weekly, or daily) reduces the principal balance by a calculated amount while also covering interest on the remaining balance. In a standard fully-amortizing loan, early payments are mostly interest (because the principal balance is high and interest accrues on the outstanding balance); later payments are mostly principal (as the balance decreases). This is the mathematical structure of all SBA 7(a) term loans, SBA 504 loans, conventional bank term loans, and most equipment financing. A 10-year fully-amortizing SBA 7(a) loan at 9% on $250,000 produces payments of approximately $3,167/month — the same payment each month, with the interest-to-principal split shifting over time until the balance reaches exactly zero at month 120. Under FASB ASC 470 (Debt), amortizing loan principal is recorded as a liability on the balance sheet and reduced with each scheduled principal payment — the interest component flows through the income statement as interest expense.

How Interest-Only Loans Work

An interest-only loan requires only the periodic interest payment during the interest-only period — no principal is paid down during this phase. At the end of the interest-only period, the borrower either pays the full principal as a lump sum (balloon payment) or converts to an amortizing schedule (often called a 'mini-perm' structure). Business lines of credit are the most common interest-only product — the borrower draws funds as needed, pays interest only on the outstanding balance, and repays the principal when cash flow allows or at the end of the draw period. Bridge loans — short-term financing used while waiting for a property sale, permanent financing, or contract payment — are typically interest-only with a lump-sum balloon. Construction loans are typically interest-only during the construction period, converting to a permanent amortizing loan at project completion. Merchant cash advances price on a factor rate (not APR) with daily or weekly ACH debits that include both implicit principal and implied cost — structurally not amortizing but also not interest-only; they are revenue-purchase agreements.

When to Use Each Structure

The right structure depends on your cash flow timing and the purpose of the financing. Interest-only fits when: cash flow is irregular (seasonal businesses, contract-based businesses), the use of funds generates a lump-sum return (bridge financing, real estate flip), or the business needs maximum flexibility during a ramp-up period. Amortizing fits when: the financing is for a long-lived asset (equipment, real estate, tenant improvements), the debt service is predictable and budgetable, or the lender requires principal reduction as a condition of the loan (SBA). Per the OCC's Comptroller's Handbook on commercial loans, most bank and SBA term loans are structured as fully amortizing — examiners favor amortizing structures because the declining principal balance reduces credit exposure over time and provides early warning signals if a borrower begins missing principal payments.

Total Cost Comparison

Interest-only financing costs more in total interest paid than amortizing financing at the same rate, because the principal balance does not decline during the interest-only period. Example: $200,000 at 9% interest for 3 years. Fully amortizing (monthly): $6,360/month, total interest $28,958. Interest-only (monthly, balloon at end): $1,500/month for 36 months, $200,000 balloon at month 36 = $54,000 total interest — nearly double. The lower monthly payment of interest-only has a real cash flow benefit during the interest-only period; the tradeoff is significantly higher total cost and a large balloon obligation. For SBA 7(a) loans specifically, the SBA does not permit interest-only structures — all SBA 7(a) and 504 loans must be fully amortizing.