Moving in with your partner is exciting — but it comes with financial changes that catch many couples off guard. From losing your single-person council tax discount to unlocking Marriage Allowance, here's everything that changes when you share a roof (and potentially a bank account).
Council tax: losing the 25% discount
If you were living alone before, you've been enjoying a 25% single-person discount on council tax. The moment a second adult moves in, that discount disappears. On a Band D property (average £2,171/year in England for 2026/27), that's an extra £543/year — or £45/month. You must inform your council immediately; failing to do so can result in backdated bills and penalties.
However, splitting the full bill between two means you each pay roughly £1,086 — less than the discounted amount for a single occupant. Financially, it's still cheaper per person.
Marriage Allowance: £252/year tax saving
If one partner earns below the Personal Allowance (£12,570) and the other is a basic-rate taxpayer (earning between £12,571 and £50,270), the lower earner can transfer £1,260 of their unused allowance to their partner. This saves the higher earner £252/year in income tax.
You must be married or in a civil partnership to claim — cohabiting couples are not eligible. You can backdate the claim by up to four years. Apply online through HMRC's Marriage Allowance service. See our Marriage Allowance guide for full details.
Joint accounts vs separate accounts
There's no single right answer, but here are the three common models:
- Fully joint: All income into one account, all bills paid from it. Simple but requires high trust and similar spending habits.
- Joint for bills, separate for personal: Each contributes a fixed amount (or proportional to income) to a shared account for rent, utilities, and food. Personal spending stays separate. Most popular approach for unmarried couples.
- Completely separate: Split bills 50/50 or proportionally via bank transfers. Maximum independence but more admin.
A proportional contribution model (e.g., each pays the same percentage of their income towards shared costs) is generally fairest when there's a significant income gap.
Tenancy agreements and financial linking
Being on a joint tenancy or mortgage creates a “financial link” on your credit file. This means your partner's credit history can affect your ability to get credit (mortgages, credit cards, loans). If your partner has poor credit, consider whether a joint tenancy is necessary — some landlords accept one named tenant with the other as a permitted occupier.
For homeowners, adding a partner to the mortgage deed has stamp duty implications if they're buying a share. Transferring equity between unmarried partners can trigger CGT (unlike married couples, who can transfer assets CGT-free).
What happens to benefits?
If either partner claims means-tested benefits (Universal Credit, Housing Benefit, Council Tax Reduction), moving in together means your combined household income is assessed. This can reduce or eliminate benefits. The DWP treats you as a couple from the moment you share a home, regardless of whether you consider the relationship serious.
Utility bills and broadband
Review your utility tariffs when moving in together. Two people use more gas, electricity, and water — but not double. Expect a 30–50% increase in usage, not 100%. Switch to dual-fuel deals and check if you can save by consolidating broadband/TV packages.
What if you split up?
Unlike married couples, cohabiting partners have very limited legal protection in England and Wales. There is no such thing as a “common-law spouse.” If you split:
- The person whose name is on the tenancy/mortgage keeps the property (regardless of who paid)
- Joint bank accounts are split 50/50 unless you can prove otherwise
- There is no automatic right to maintenance or a share of your partner's pension
Consider a cohabitation agreement (similar to a prenup) that sets out who owns what and how assets would be divided. These are not automatically legally binding but carry significant weight in court.
Tax-efficient strategies for couples
- Transfer savings to the lower earner to use their Personal Savings Allowance (£1,000 for basic-rate vs £500 for higher-rate)
- Hold investments in the name of the partner with the lower CGT rate
- If one partner is a non-taxpayer, they can receive up to £18,570 in income (£12,570 + £5,000 starting rate + £1,000 PSA) with zero tax on savings interest
- Use both ISA allowances: that's £40,000/year combined shelter from tax
Check your combined position
Use the income tax calculator to check both your individual take-home figures and plan your contribution split. If you're getting married, our Marriage Allowance guide shows you how to claim your £252 saving.