Understanding Your Amortisation Schedule

An amortisation schedule is a table that shows every payment over the life of a loan. It breaks down each payment into how much goes toward interest, how much reduces the principal, and what the remaining balance is after each payment. Understanding this table helps you track your real progress in paying off debt and make informed financial decisions throughout the life of your loan.

The columns explained

Each row in the schedule represents one payment. For a monthly loan, each row corresponds to one month. Understanding what each column represents helps you interpret your loan's progress:

• Payment number: The sequence count (1, 2, 3… n). This tracks where you are in the loan term and helps you identify specific payments when reviewing your history.
• Payment amount: The fixed monthly payment (constant throughout in French amortisation). This is the total amount you pay each period, which remains unchanged even as the internal split between interest and principal varies.
• Interest portion: The part of the payment that goes to interest for that period. This is calculated by multiplying the remaining balance by the periodic interest rate. It starts high and decreases over time.
• Principal portion: The part that reduces the outstanding balance. This starts small and grows larger as the interest portion shrinks, accelerating your equity building over time.
• Remaining balance: The amount owed after the payment is applied. Watching this column decrease shows your progress toward full repayment and helps you understand how much you still owe at any point.

Some schedules also include a running total of interest paid, which can be eye-opening. Seeing that you have paid £50,000 in interest over five years while only reducing principal by £25,000 illustrates why early extra payments are so powerful.

How interest and principal shift

In French amortisation, the payment is fixed, but its composition changes dramatically over time. Early payments are mostly interest; late payments are mostly principal. This happens because interest is calculated on the remaining balance, which is highest at the start.

Consider the first few months of a £200,000 mortgage at 6% EAR over 30 years (360 monthly payments). The periodic rate is roughly 0.00487 per month. In month 1, the interest on a £200,000 balance is approximately £974. The remaining £373 of the payment reduces the principal. By month 180 (year 15), the balance is much lower, so the interest portion shrinks to about £570 while the principal portion grows to £777.

This shifting composition means that the same £1,347 monthly payment builds equity slowly at first but accelerates significantly in later years. Understanding this pattern helps you evaluate strategies like refinancing or making extra payments.

The crossover point

There is a point in every amortisation schedule where interest and principal portions are equal. For a 30-year mortgage at 6%, this happens somewhere around year 12 or 13. Before this crossover point, you are paying more in interest than you are reducing principal. After it, the principal reduction accelerates.

This has practical implications for extra payments. Making extra payments before the crossover point has a much larger impact on total interest paid than the same extra payments made later, because early extra payments skip all the future interest on that amount. A £1,000 extra payment in year 2 might save you £3,000 in total interest, while the same payment in year 20 might save only £500.

How to use your schedule

Beyond simply tracking payments, your amortisation schedule is a valuable tool for financial planning:

Tax deduction planning

If you itemise deductions and can deduct mortgage interest, your schedule shows exactly how much interest you will pay each year. This helps you estimate your tax deduction and plan accordingly. In the early years of a mortgage, when interest payments are highest, this deduction can be substantial.

Refinancing timing decisions

Your schedule helps you evaluate whether refinancing makes sense. If you have already passed the crossover point and are building equity rapidly, refinancing to a new 30-year loan resets the clock and puts you back into high-interest payments. Use your schedule to calculate the break-even point for refinancing costs versus interest savings.

Mistakes to avoid

Many borrowers misunderstand their amortisation schedule, leading to costly errors:

• Ignoring the early years: The first five years of a 30-year mortgage are where extra payments have the most impact. Waiting until year 10 to start making extra payments leaves significant savings on the table.
• Refinancing without considering reset: Refinancing resets your amortisation schedule. Even at a lower rate, starting over with a new 30-year term means returning to interest-heavy payments.
• Not verifying extra payment application: When making extra payments, ensure your lender applies them to principal immediately rather than holding them for future payments or applying them to escrow.

Reading your own schedule

When you run a calculation in Amorta, the schedule table shows exactly these columns for each payment interval. You can see the cumulative interest paid at the bottom of the table, which helps you understand the true cost of the loan over its full term.

Pay attention to the interest column in the early rows to see how much of your payment is "wasted" on interest versus building equity. This perspective helps when evaluating whether to make extra payments or when comparing loan offers. Look at your remaining balance column to track your progress and set milestones for your payoff journey.

Regularly reviewing your schedule keeps you engaged with your debt payoff progress and helps you identify opportunities to save money through strategic extra payments or refinancing decisions.