Interest Only and Amortization | How the Schedule Drives the Payment

Definition

Interest only. Each payment covers the interest accrued on the outstanding balance and nothing more. Principal is untouched, so the balance at the end of an interest only period is identical to the balance at the start.

Amortization. Each payment covers interest plus a portion of principal, calculated so that the balance would reach zero across a defined schedule. Early payments are mostly interest; the principal share grows over time.

Amortization period against loan term. These are separate numbers and confusing them is expensive.

- The term is how long the loan actually runs before the full remaining balance is due. - The amortization period is the notional schedule used to size the principal component of the payment, commonly 20, 25 or 30 years on commercial debt.

When the amortization period is longer than the term, which is the normal case, the loan does not fully pay off during its life. Whatever is left at maturity is the balloon, and repaying or refinancing it is the borrower's problem to solve long before it arrives.

The Chain: Schedule to Payment to Coverage

The reason this matters is a short causal chain that runs in one direction.

The schedule sets the payment. Interest only produces the smallest payment. A 30 year amortization produces a smaller payment than a 25 year, which produces a smaller payment than a 20 year, all on the same balance at the same rate.

The payment sets the coverage ratio. Debt service coverage ratio is net operating income divided by annual debt service. Debt service is the payment. So a smaller payment mechanically produces a higher ratio.

The coverage ratio sets the loan size. Most lenders size to a minimum coverage floor and lend the amount that clears it.

Run that chain backwards and the risk becomes obvious: a longer schedule raises the coverage ratio, which supports a larger loan, without any change in what the property actually earns. The ratio improved. The asset did not.

This is not a scandal, it is arithmetic, and legitimate deals use it deliberately. The problem is when a coverage ratio is presented as evidence of a property's strength while the schedule doing the work goes unmentioned.

What the Illustration Shows

In the table above nothing about the property changes. Same $10,000,000 balance, same rate, same $1,000,000 of net operating income across every row. Only the schedule moves.

On interest only the deal shows roughly 1.28x coverage and clears a 1.25x floor. Put the same loan on a 30 year amortization and coverage falls to roughly 1.08x, which does not clear. On a 20 year schedule it falls below 1.00x, meaning the property does not cover its own debt service at all.

The practical reading for a sponsor:

If your coverage clears only on interest only, you do not have 1.28x coverage. You have a 1.08x asset with a payment holiday. That is fine when the holiday is matched to a plan that raises income before it ends. It is not fine when the plan is simply that the numbers looked better this way.

Model the step up before you close. Work out the payment and the coverage the month amortization begins, and satisfy yourself the property will be earning enough by then. If the loan is also floating rate, model it with the index higher than today, because the payment step up and a rate reset can arrive together.

When Interest Only Is the Right Structure

Interest only earns its place when the asset genuinely is not producing its stabilized income yet and there is a real plan to get it there.

Construction. There is no income at all during the build. Interest only for the whole term is standard, frequently funded from an interest reserve inside the loan rather than out of sponsor cash.

Lease up. A newly delivered asset filling to stabilized occupancy needs a payment matched to the income it has now, not the income it will have.

Repositioning and value add. Units or suites are offline during work. Income is temporarily depressed by design.

Early years of a stabilized permanent loan. A defined interest only period at the front of a longer term loan, with amortization following, is a common and unremarkable structure on strong assets.

The honest test is simple: is the interest only period matched to a business plan with a provable end point, or is it making a payment affordable that otherwise would not be? The first is structure. The second is a problem moved to a later date, usually a date when a balloon is also due.

Why Lenders Do Not Trust Coverage Alone

Everything on this page is well understood by the people underwriting the deal, which is exactly why the coverage ratio is not the only test a loan has to pass.

Debt yield is net operating income divided by loan amount. It contains no payment, no rate and no schedule, so it cannot be improved by stretching amortization or adding an interest only period. Whatever the schedule, the debt yield is the same number. In current commercial real estate conditions it is doing more of the binding than loan to value is, and on many conduit deals it sets the loan size outright.

Leverage caps run alongside. Across what lenders in the PeerSense network have demonstrated, 65 percent is the realistic anchor: commercial broadly 60 to 65 percent, residential 70 to 75 percent, and bridge lower than either. Above 75 percent is not a level we publish as an expectation, and every leverage figure we publish states whether it is against value, against cost, or against after repair value.

Coverage floors still matter enormously. Coverage below 1.25x remains the single most common reason a deal does not clear.

A lender running all three together is protecting itself against exactly the flattery this page describes. A sponsor who runs all three on their own deal before going to market finds out what is real while there is still time to do something about it.

Sizing, structure and approval are the lender's decision. PeerSense is a capital advisory: we position a deal and place it with lenders whose credit box already fits it. We do not lend, fund, price or approve anything.