Read the ownership agreement alongside the mortgage
The title records ownership; the mortgage documents record borrowing obligations. Gather both, together with any agreement made when you bought the home. A promise between partners about paying the mortgage does not itself release either borrower.
Unmarried co-owners should not assume that divorce rules apply, or that no rules apply. The property’s location, ownership arrangement and agreements affect the advice you need.
Trace the contributions you want the split to recognise
For each deposit or later payment, record the amount, date, payer and source of funds. Distinguish individual savings from joint funds and family money described as a gift or loan. Payment evidence helps establish what happened; its legal treatment may still need advice.
If one person owned the home before the relationship, record the purchase history and what changed when the other became involved. Later payments should not be silently treated as a purchase of half the property. Establish the proposed treatment with the relevant adviser before entering a percentage or contribution credit.
The unequal down payment methods address purchase contributions. For later repayments, splitting equity after unequal mortgage payments explains which part reduced the loan.
Put a complete buyout proposal to your co-owner
Agree a valuation date and enter the debt once. Use the house buyout calculator to compare a selected percentage with contribution credits. Record why you chose that method so the other person can review more than the final number.
The proposal also needs a funding deadline and an alternative if the buyout cannot complete. Ask the lender about its requirements before promising a release from the mortgage. Obtain local advice on the agreement and transfer documents.
If the disagreement is about whether the property should be sold at all, read options when a co-owner refuses to sell. Another calculation will not resolve that decision.