How to split mortgage and bills when one paid a bigger deposit
Deposit differences matter — but they don’t automatically tell you what the monthly split should be. A calm approach separates two problems: ownership/equity (deposit contribution) and monthly affordability (mortgage + bills). This guide focuses on the monthly side: making sure both people have sustainable leftovers and the plan passes stress tests.
Run a deposit-heavy scenario and compare splits
Opens the main calculator prefilled so you can compare proportional vs custom splits and check leftovers and stress tests.
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Three reasonable ways couples handle it
- Separate the problems: agree ownership/equity separately, then split monthly costs by income (or 50/50) for sustainability.
- Custom monthly split: pick a custom % that reflects both affordability and deposit contribution, then review over time.
- Hybrid: mortgage split one way (e.g. proportional), bills split another (e.g. 50/50), to match what feels fair and simple.
This is budgeting guidance only — not legal or financial advice. If you need legal clarity about ownership, speak to a solicitor.
Worked examples (same home, different split)
Both examples use the same property and deposit, then compare a proportional split to a custom split.
Example 1: larger deposit, but monthly costs still proportional
Home £500,000 · Deposit £140,000 · Loan £360,000
Total shared cost: £3,196 / month
Proportional
A £2,034 · B £1,162
50 / 50
A £1,598 · B £1,598
Selected mode: proportional · Leftovers: A £2,166 / B £1,238
Example 2: custom split to reflect deposit contribution
Home £500,000 · Deposit £140,000 · Loan £360,000
Total shared cost: £3,196 / month
Proportional
A £2,034 · B £1,162
50 / 50
A £1,598 · B £1,598
Selected mode: custom · Leftovers: A £2,282 / B £1,122
A practical “fairness” checklist
- Does each person have enough leftover to live and save?
- Does the plan survive +1% and +2% rates?
- Could one income cover shared costs temporarily?
- Have you explicitly discussed the deposit as a separate topic?
FAQ
Should the deposit affect monthly payments?
Sometimes. The deposit is about equity and risk; the monthly split is about affordability. Many couples keep monthly costs proportional (or 50/50) and treat the deposit separately as an ownership/equity agreement.
Can the higher-deposit person pay less monthly?
That’s one valid option — but only if it stays sustainable for the other person. The calculator helps you test whether the lower earner still has a healthy leftover and whether the plan passes stress tests.
Is this legal advice about ownership splits?
No. This page is budgeting guidance about monthly affordability. Ownership and legal arrangements are separate; speak to a solicitor for legal advice.
What if we break up?
That’s exactly why it helps to make contributions explicit and documented. This tool can help you agree a fair monthly plan, but it’s not a substitute for legal guidance.
Explore related UK guides
Quick links: partner moves in later, partner earns more — what’s fair?, how much deposit do we need.
Related guides
Mortgage & bills split calculator
Run your numbers live and share a scenario link.
50/50 vs proportional vs custom splits
Choose a split that feels fair and stays sustainable.
Stress test for rate rises and one income
+1% / +2% and one-income checks in plain English.
Split the mortgage by income (UK)
Proportional splits explained with worked examples.
Proportional bills split calculator guide
Turn take-home pay into a clean monthly split.
66/33 vs 50/50 split for couples
When a custom split beats proportional (and when it doesn’t).
How much house can we afford (and still save)?
Affordability framing using leftovers + a savings goal.
Stamp Duty (SDLT) calculator for couples
Standard vs first-time buyer relief + surcharges.
60/40 bills split guide
A simple compromise between 50/50 and proportional.
70/30 bills split guide
When a fixed split makes sense (and how to validate it).
Tip: open a guide in one tab and the calculator in another to compare options quickly.