How to Claim Cornwall Council Tax Reduction When an Adult Child Moves Home

When an adult child moves back into your Cornwall home, your council tax bill can jump overnight — you may lose the 25% Single Person Discount if they count for Council Tax purposes, and a non-dependant deduction may reduce your Council Tax Reduction. The combined hit can add hundreds of pounds a year to your bill. Here's exactly what changes, what exemptions might apply, and how to handle the council.

What Happens to Your Bill

Two things change simultaneously when another adult joins your household in Cornwall:

The Single Person Discount may end. If you were the only adult counted for Council Tax, a second adult who is also counted usually ends the 25% discount. Some people, including full-time students (though Cornwall may count them if they work during summer months), people under 18, and people with a qualifying severe mental impairment, are disregarded, so their moving in does not automatically end the discount. On a Band D property in Cornwall (roughly £2,200 for 2026/27), losing the discount adds about £550 a year to your bill.

A non-dependant deduction may reduce your CTR award. If you're claiming Council Tax Reduction, Cornwall Council assumes that other adults in your household contribute to the bill. They deduct a set weekly amount from your CTR award based on the non-dependant's gross income — regardless of whether that person actually pays you anything.

The 2026/27 non-dependant deduction is £5.00 per week for someone aged 18 or over who is not in paid work. It rises to £15.95 per week when a working non-dependant has gross weekly income of £577 or more — about £829 a year at the top rate.

When Deductions Don't Apply

Not every adult moving in triggers a deduction. Cornwall does not apply one in these circumstances:

• You or your partner receive Attendance Allowance, the care component of Disability Living Allowance, the daily living component of Personal Independence Payment, or Armed Forces Independence Payment, or are blind or treated as blind
• The non-dependant is under 18, a full-time student (though Cornwall may count them if they work during summer months), receives State Pension Credit (including Guarantee Credit), or is disregarded for Council Tax purposes because of a qualifying severe mental impairment
• The non-dependant is a paid care worker provided by a charity or commercial agency

A Universal Credit award with no earned income is not, by itself, a listed exemption in Cornwall's scheme.

If you think an exemption applies, tell Cornwall Council and provide supporting evidence if asked. For student status, for example, the Council lists a college or university enrolment letter as household-composition evidence.

The Practical Steps

1. Report the Change Immediately

If you receive CTR, Cornwall's scheme requires you to report changes that may affect entitlement within 21 days. If a late report results in excess Council Tax Reduction, the council adjusts the account retrospectively and issues a revised demand notice; it is not recovered as a Housing Benefit overpayment.

2. Check Whether You Still Qualify for CTR

Even with a non-dependant deduction, you may still qualify for Council Tax Reduction. Cornwall's scheme assesses your household income against your applicable amount. The deduction reduces your award, but it doesn't automatically disqualify you. Run the numbers: if your income is low enough, the remaining CTR award after the deduction could still save you hundreds.

3. Gather the Right Evidence

If you think a non-dependant exemption applies, tell Cornwall Council and provide the evidence it asks for. For example:

• Student: a certificate of attendance from the university or college
• State Pension Credit: a current award statement
• Qualifying severe mental impairment: the medical and benefit evidence required for Council Tax disregard

4. Apply for CTR If You Haven't Already

If the lost Single Person Discount pushes your household into financial difficulty, you may now qualify for Council Tax Reduction even if you didn't before. The CTR application is free through Cornwall Council's online portal. Remember Cornwall's zero-backdating rule: your award normally starts from the Monday following the date the council treats your claim as made. If your Council Tax liability first begins in the same reduction week, the award starts from the date that liability began; it cannot be backdated to when your child moved in.

Who This Is For

• Single parents in Cornwall whose adult child has moved back home after university, a relationship breakdown, or redundancy
• Households that just lost the Single Person Discount and want to understand whether CTR can offset the increase
• Cornwall residents already on CTR who need to report a household change and want to know how the non-dependant deduction will affect their award
• Family members trying to work out the cheapest honest arrangement when an adult returns to the household

Who This Is NOT For

• Households where the person moving in is under 18 — they are disregarded for Council Tax purposes, so they do not by themselves end a single-person discount or trigger a non-dependant deduction
• Pension-age households — the pensioner CTR scheme has different non-dependant deduction rules and higher capital limits
• Anyone with council tax arrears or enforcement action — contact StepChange (0800 138 1111), National Debtline (0808 808 4000), or Citizens Advice Cornwall's Debt Helpline (0800 240 4420) for free debt advice first

The Financial Arithmetic

Here's a realistic scenario for a Cornwall household:

You're a single adult in a Band C property. Your annual council tax is about £1,960. With the 25% Single Person Discount, you pay £1,470. Your adult child, who is 18 or over, is not disregarded for Council Tax purposes and is not in paid work, moves in.

• You lose the Single Person Discount: bill goes from £1,470 to £1,960 (+£490/year)
• If you qualify for CTR at the maximum 75% cap: your reduction covers up to £1,470 of the £1,960
• If no non-dependant exemption applies, Cornwall's £5 weekly deduction for an adult who is not in paid work reduces your CTR award
• Net result: you could end up paying less than you were before, depending on your own income

The numbers depend entirely on your income, savings (which must not exceed £6,000), and whether the non-dependant qualifies for an exemption. The Cornwall Council Tax Reduction Guide includes the full non-dependant deduction table and three worked scenarios you can follow with your own figures.

The Common Mistakes

Not reporting the change. CTR claimants must tell Cornwall Council within 21 days about changes that may affect entitlement. If a late report results in excess support, the council can adjust the council tax account retrospectively and issue a revised bill.

Assuming the non-dependant's income doesn't matter. Even if your child doesn't contribute to the bill, the council deducts based on their income. If they start working, report the change to the council within 21 days.

Forgetting to claim CTR. Many people who lose the Single Person Discount don't realise they might qualify for Council Tax Reduction. If your household income is low, CTR could more than offset the lost discount.

Waiting to apply. Cornwall's zero-backdating policy means every week between the household change and your CTR application is lost support.

Frequently Asked Questions

Will my council tax definitely go up when my adult child moves home?

If you have the Single Person Discount, yes — you'll lose it. But if you or your household now qualifies for Council Tax Reduction, the CTR award could offset some or all of the increase. The net effect depends on your income and your child's circumstances.

Does my child have to pay anything towards the council tax?

There's no legal requirement for a non-dependant to pay you. But Cornwall Council will deduct an amount from your CTR award as if they contribute, based on their gross income. The deduction applies regardless of whether money actually changes hands.

What if my child moves out again after a few months?

Report the change to Cornwall Council. If you're the only adult counted for Council Tax, your Single Person Discount may be reinstated from the date of the change. If you claimed CTR, the non-dependant deduction will be removed from your award going forward.

Can I backdate my CTR claim to when my child moved in?

No. Cornwall's working-age scheme does not allow backdating. Your award normally starts from the Monday following the date the council treats your claim as made. If your Council Tax liability first begins in the same reduction week, the award starts from the date that liability began. This is why reporting and applying promptly is important.

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