When you take out home insurance, you expect your policy to give you peace of mind. But many people don’t realise that even with a policy in place, they could still be at risk of underinsurance: a gap in cover that could leave you unexpectedly out of pocket.
At the same time, many policies include something called index linking, which is designed to keep your cover in line with rising prices and inflation. Understanding these two areas can make a big difference in how well your home and belongings are protected.
This guide explains both topics in simple, practical terms. Whether you’re new to home insurance, checking your sums insured, or reviewing your Acorn Insurance policy, this article will walk you through everything you need to know.
What Is Underinsurance?
Underinsurance happens when the amount you have insured your buildings or contents for is less than the true cost to rebuild or replace them.
This means that even though you have a policy, your payout may be reduced if the sums insured are too low (sums insured refers to the maximum amount your insurer will pay for buildings or contents in the event of a claim). If the sum insured is too low or over their limit, some insurers may not pay the claim at all, and the policy can be voided. Many people only find out they’re underinsured at the point of making a claim — when it matters most.
A simple way to think about it
If your policy doesn’t fully reflect the value of what you own, you may not receive the full amount needed to repair, rebuild or replace it.
Underinsurance can affect:
- Buildings insurance – if the rebuild cost of your home has been underestimated
- Contents insurance – if the total value of everything in your home hasn’t been kept up to date
- High-value items – if these items haven’t been individually listed where required or they have been listed, but the value is not correct.
How Underinsurance Is Assessed Under Consumer Insurance Law
For household insurance policies, claims are assessed in line with UK consumer insurance law rather than an automatic “average rule”.
This means that if the amount insured does not reflect the true cost of rebuilding your home or replacing your contents, your insurer will look at how the information was provided and what would have applied if the correct details had been given at the time the policy was taken out or renewed.
If a difference is identified:
- The insurer may adjust the claim outcome to reflect the cover and premium that would have applied originally
- In some cases, the settlement may be reduced to reflect the difference between the premium paid and the premium that would have been charged if the correct sums insured had been declared
- Any adjustment is made proportionately and fairly, based on the circumstances
- Honest mistakes are treated differently from deliberate or reckless misrepresentation
In some situations, where the information provided means the risk would not have been acceptable to insure, the policy may be voided (treated as if it had never existed) and any claims may be rejected.
Understanding the above is key to making sure your sums insured reflect your true costs.
Why Underinsurance Happens
Underinsurance can creep in slowly, often without people noticing. Common causes include:
1. Underestimating rebuild costs
The rebuild cost of a home is not the same as its market value. Rebuild costs include labour, materials, professional fees and more, and can be significantly higher if your home is a Grade Listed property.
2. Rising prices
Construction materials, labour and household goods often increase in price each year.
3. New belongings or upgrades
Replacing furniture, buying new tech, or improving your home can all increase the value you need to insure.
4. Renovations and extensions
Extensions, new kitchens, outbuildings or garden rooms all increase rebuild costs. It’s important to let your insurer know about any works carried out so they can help ensure your cover remains appropriate. If you’re not sure, please contact your insurance company’s customer service team for guidance. (If you’re an Acorn Insurance customer, you can contact us on 0330 331 0749 (Monday–Friday, 09:00–17:30).
5. High-value items not listed separately
Many policies have a “single item limit.” If something you own is worth more than that limit, it usually needs to be specified on your policy.
What Is Index Linking?
Index linking (also called indexation) is a way insurers keep the sums insured on your home insurance policy aligned with inflation and rising costs.
How index linking works
Depending on your insurer and policy terms, sums insured may be adjusted each year using recognised inflation indices, such as:
- The House Rebuilding Cost Index – for buildings
- Retail Price Index – for contents
These adjustments help ensure your cover keeps place with real-world costs, reducing the risk of becoming underinsured over time.
Important to know
Index linking only works properly if your starting sums insured are accurate.
If the amount you initially chose is too low, index linking increases an incorrect figure. That’s why regularly reviewing your sums insured is so important.
High-Value and Specified Items
Home insurance policies can have:
- A contents sum insured – the total amount covered for all belongings
- A single-item limit – the maximum value for any one item before it must be listed separately
Common high-value items include:
- Jewellery and watches
- Bicycles
- Designer handbags and clothing
- Laptops and cameras
- Art or collectibles
- Musical instruments
If a high-value item is worth more than your policy’s single-item limit, it usually needs to be specified. If it isn’t, the amount paid out in a claim may be limited or the claim may not be covered at all.
How to Check Whether You’re Underinsured
You can reduce the risk of underinsurance by taking a few simple steps:
1. Get an accurate rebuild estimate
Use a rebuild cost calculator (such as the online calculator provided by Building Cost Information Service) or consult a professional surveyor.
2. Review your contents value
Go room by room and list everything you own. You may find the total is higher than expected.
3. Keep valuations up to date
Items like jewellery and collectibles can increase in value over time.
4. Check your policy’s single-item limit
Make sure any valuable belongings are correctly listed.
5. Review your policy regularly
Renewal is a useful reminder to check your sums insured still reflect your needs. However, you should also review your cover whenever your circumstances change; for example, when making home improvements, major purchases, or if rebuild or replacement costs increase.
Information if You Have Bought a Household Insurance Policy with Acorn Insurance
If you’re an Acorn Insurance customer, or you’ve landed on this page through one of our emails, the information below explains how index linking and underinsurance apply specifically to your household policy.
How Index Linking Works on Your Acorn Home Insurance Policy
Each year, your renewal quote will be index linked, unless you choose to opt out (please see section below: ‘If you wish to opt out of index linking).
This means your sums insured (sums insured refers to the maximum amount your insurer will pay for buildings or contents in the event of a claim) for:
- Buildings are adjusted in line with the House Rebuilding Cost Index (published by the Royal Institution of Chartered Surveyors)
- Contents are adjusted in line with the Retail Price Index (published by the Office for National Statistics)
Index linking is designed to help keep your cover in line with inflation so that your policy remains suitable without you needing to manually calculate inflation changes yourself.
Why checking your sums insured still matters
For index linking to work correctly, your original sums insured must be adequate.
Index linking cannot correct an amount that was too low to begin with.
We encourage you to regularly check that your cover reflects your current circumstances, particularly at renewal, but also whenever things change (such as an extension to the property). This includes reviewing:
- The rebuild cost of your home
- The total replacement cost of your contents
- The value of any specified items
This helps reduce the risk of being underinsured.
If you wish to opt out of index linking
You can contact us on 0330 331 0749 (Monday–Friday, 09:00–17:30).
If you choose to opt out of index linking, your sums insured will no longer automatically increase in line with inflation.
This means you would need to regularly review:
- The rebuild cost of your home
- The replacement cost of your contents
- The value of any specified items
If these amounts are not kept up to date and costs increase over time, there is a greater risk of becoming underinsured. This could affect how a claim is assessed.
Opting out is entirely your choice — we’re here to support you either way.
Understanding Underinsurance on Your Policy with Acorn Insurance
If your home or belongings are insured for less than their true value, a claim may be reduced in line with the proportion of underinsurance and sometimes may not be paid at all.
If you have purchased your policy with Acorn Insurance, you will be able to find your sums insured amount on your Statement of Fact (SoF) or Schedule.
Buildings Insurance: What’s included in the rebuild cost?
This section is applicable if you have chosen to purchase buildings only or buildings and contents insurance. Your rebuild value should cover:
- The structure of your home
- Fixtures and fittings
- Carpets and fixed flooring
- Solar panels
- Garden structures such as patios, terraces, driveways, walls, gates and paths
- Permanently fixed features like fountains or hot tubs
- Debris removal
- Architects’ and surveyors’ fees
- Legal costs and VAT
- Any additional expenses needed to comply with building regulations
- All outbuildings including attached and detached garages
- Aerials, satellite dishes and fittings
If the sum insured does not cover the true rebuild cost, the settlement for a claim may be reduced or the claim may not be paid at all.
Contents Insurance and Specified Items
This section is applicable if you have chosen to purchase contents only or buildings and contents insurance. Your contents sum insured should reflect the full replacement cost of:
- Clothing and belongings
- Furniture and household goods
- Electronics and appliances
- High-risk or high-value items
- Money, credit cards and business equipment kept at home
If your contents are underinsured, your claim may be reduced in line with the level of underinsurance or may not be paid at all.
This also applies to any specified items on your policy.
Final Thoughts
Underinsurance and index linking may feel like technical topics but understanding them can make a real difference to the level of protection your home insurance provides.
By:
- Reviewing your sums insured
- Getting accurate valuations
- Understanding how index linking affects your cover
- Listing high-value items correctly
- Updating your policy after changes
…you can help ensure your home and belongings are protected in a way that reflects your needs.
Whether you are reviewing your existing policy arranged by Acorn Insurance or comparing insurance options for the first time, we’re here to support you in making informed, confident decisions.
If need help or wish to review your cover, you can contact us on 0330 331 0749 (Monday- Friday: 09:00 to 17:30).