A home purchased before marriage generally begins as the purchasing spouse’s separate property. However, when community earnings are used during marriage to reduce the mortgage principal, the community may acquire a proportional interest in the property.

This calculation is commonly known as a Moore-Marsden apportionment.

Principal Payments Create the Interest

The community interest generally arises from community funds applied toward the property’s purchase price, including mortgage principal reduction.

Payments for interest, property taxes, insurance, and ordinary maintenance ordinarily do not create the same proportional ownership interest because they do not increase equity by paying down the purchase price.

Records should therefore distinguish principal reduction from the total amount of each mortgage payment.

Appreciation Is Allocated Proportionally

The separate estate ordinarily retains the owner’s initial equity and appreciation attributable to the separate interest. The community receives credit for principal paid with community funds and a proportional share of appreciation during the marriage.

The calculation may require:

• The original purchase price
• The down payment
• Principal owed on the date of marriage
• The property’s value on the date of marriage
• Community principal payments
• The separation date
• The value near trial

A retrospective appraisal may be needed when reliable historical values are unavailable.

Refinancing Can Complicate the Calculation

The character of a refinance depends on the source of the new credit and how the proceeds were used. A refinance does not necessarily eliminate an existing community interest.

Cash withdrawals, capital improvements, title changes, and postseparation payments may create additional characterization or reimbursement issues that should be evaluated separately.

Ownership and Reimbursement Are Different Concepts

When community funds pay the debt on separate property, the remedy generally involves proportional apportionment. When separate funds are used to acquire community property, the remedy may instead involve reimbursement.

A California property division attorney can obtain mortgage histories, appraisals, deeds, and refinance documents to calculate the interests accurately. Treating the home as entirely separate or automatically half community can both produce an incorrect result.