Learn what each section of a mortgage illustration (ESIS) means for buy-to-let: rates, fees, ICR, stress tests, and risks. Read it confidently and compare lenders like for like.
If you’ve ever been handed a mortgage illustration (also called an ESIS) and thought “this looks important… but what does it actually mean?”, you’re not alone.
The good news is that once you know how it’s laid out, an ESIS becomes a really useful tool. It’s designed to help you compare mortgages clearly and confidently, especially for buy-to-let deals where the detail really matters.
Let’s walk through it in plain English, section by section, so you can read one without second-guessing yourself.
First things first: what is an ESIS?
ESIS stands for European Standardised Information Sheet. It’s a standard document that every lender uses, which means you can compare different mortgages on a like-for-like basis.
Think of it as the “full breakdown” of a mortgage before you commit.
1. The basics: who, what, and how much
At the top of the mortgage illustration (ESIS), you’re basically just checking you’re looking at the right deal.
It will show the lender, how much you’re borrowing, the property value, and how long the mortgage runs for. Nothing complicated here, but it’s surprising how often people skim past it.
If any of these details are slightly off, everything else in the document won’t quite line up. So it’s worth pausing for a moment and making sure it all matches what you expected.
2. The interest rate: what you’re actually signing up for
This is usually the first thing people look at, and for good reason.
You’ll see an initial rate (often fixed for a few years), followed by what happens afterwards. That second part is easy to overlook, but it matters just as much.
A deal might look great on day one, but the real question is how it behaves over time. Once you get into the habit of checking both the starting rate and the follow-on rate, things start to make a lot more sense.
For buy-to-let, this isn’t just about payments, it feeds directly into whether the deal works as an investment.
3. Monthly payments: what it feels like in real life
This section tends to make things click.
Instead of percentages and terms, you’re looking at actual monthly numbers, what you’ll pay at the start, and what it could look like later on.
It’s completely normal for the future payment to be higher. That’s not the lender being sneaky, it’s just how most mortgage structures work.
The useful way to read this is simply to ask yourself: would this still feel comfortable if things changed? If the answer is yes, you’re in a strong position.
4. Fees and costs: the bits people often underestimate
This is where the detail sits.
You’ll see all the extra costs attached to the mortgage: arrangement fees, valuations, sometimes legal costs, and any charges for exiting early.
It can look like a long list, but it’s actually doing you a favour by putting everything in one place.
With buy-to-let especially, the cheapest rate isn’t always the best deal once fees are factored in. Sometimes a slightly higher rate with lower fees works out better overall, it just depends on your plan.
5. APRC: the “true cost” snapshot
You’ll come across something called the APRC (Annual Percentage Rate of Charge).
It’s basically a way of showing the total cost of the mortgage over time, including fees and interest.
It’s useful for comparing deals, but don’t rely on it alone, especially if you don’t plan to keep the mortgage for the full term. Still, it gives a helpful “big picture” view.
6. Buy-to-let specifics: ICR and stress testing
Now we get into the parts that matter most for landlords.
ICR (Interest Coverage Ratio)
This tells you whether the expected rental income covers the mortgage payments.
Lenders use it to decide if the deal is affordable. For example, they might require the rent to be 125% or 145% of the mortgage interest.
When you read this section, you’re really checking: “Does this deal stack up as an investment?”
Stress testing
Lenders don’t just look at today’s rate, they test your mortgage against a higher “stress rate” to make sure it would still be affordable if rates rise.
This might seem strict, but it’s actually a positive thing. It helps ensure your investment remains sustainable, even if the market changes.
7. Risks and warnings: don’t just skip this bit
This is usually the section people rush through, but it’s actually one of the more useful parts once you slow down.
It covers things like what happens if rates go up, or if payments are missed, and how variable rates can change over time.
None of it is there to scare you. It’s just laying everything out clearly so there are no surprises later on.
If anything, it’s a good sense check. It helps you step back and think, “am I comfortable with how this could play out?”
8. Early repayment charges: thinking a step ahead
This part matters more than most people expect, especially if you don’t plan to keep the mortgage forever.
It explains whether you can repay early, switch deals, or exit, and what it might cost to do that.
Some mortgages are quite flexible, others less so. The key is knowing where you stand before you need to make a move.
If you’re likely to refinance, sell, or restructure in a few years, this section is worth paying proper attention to. It can make a bigger difference than the headline rate in some cases.
Bringing it all together
Reading a mortgage illustration (ESIS) might feel technical at first, but it’s actually designed to give you confidence.
Once you know where to look, you can quickly answer the key questions:
- What will this cost me now and later?
- How does it affect my rental income?
- Are the fees worth it?
- Can I exit the deal if I need to?
And most importantly, you can compare different lenders properly, apples with apples, not apples with oranges. For extra help you can also visit MoneyHelper.
Final thoughts
A mortgage illustration (ESIS) isn’t just paperwork, it’s your roadmap.
The more comfortable you get reading it, the more in control you’ll feel when choosing a mortgage. And that’s especially valuable in buy-to-let, where small details can make a big difference to your returns.
Take your time with it, ask questions where needed, and treat it as a tool, not an obstacle. Once it clicks, it really does make things clearer.
To begin your investment journey or add to your portfolio visit 365 Invest or get in touch through our contact page, we’re always happy to help.
