When co-owners dispute "who paid what," the honest answer almost never lives in anyone's memory—it lives in bank statements. A defensible contribution analysis starts with a transaction-level master ledger: every property-related payment from acquisition forward, each line tied to a date, a payor, a category, and a source document.
Three methodological choices drive the result more than anything else. First, categorization: net capital at closing, mortgage principal, interest, taxes, insurance, and improvements are not interchangeable, and different equity frameworks credit them differently. A ledger that lumps them together can't answer the questions the court will actually ask. Second, attribution: a payment counts for the party whose funds made it, which means tracing to the originating account—joint-account payments need a funding analysis of their own, and transfers between the parties must be netted so nothing is counted twice. Third, the cutoff date: separation, move-out, and filing dates can be years apart, and which one anchors the analysis often swings the ratio materially.
The output worth paying for is not a single number but a periodized picture: contributions by category, by party, by period, with a documentation-coverage rate stated plainly. When 95%+ of ledger dollars trace to bank or settlement evidence, the ratio stops being an argument and starts being a fact opposing counsel has to work around.