After separation, one spouse often keeps paying the mortgage on a jointly owned home. Whether and how a court credits those payments differs across DC, Maryland, and Virginia, and it is counsel's argument to make. The accountant's job is to make sure the credit can be computed from source documents under whichever rule applies.
Split the payment
A mortgage payment is four things: principal, interest, taxes, and insurance. Principal reduces the loan and increases equity. The other three are carrying costs. Frameworks differ on which parts earn a credit, so the ledger tracks all four separately, month by month, from the lender's statements and escrow analyses rather than from the bank withdrawal.
Offsets that come back the other way
The paying spouse usually lived in the house. The other spouse may have paid other shared costs instead. Rental income may have come in. Each of these is a potential offset, and the analysis should compute them with the same rigor as the credit itself. Apply the same logic in both directions: if carrying costs count when one spouse paid them, they count when the other did. Asymmetric treatment is the first thing an opposing expert looks for.
The date does the work
Every month the separation date moves changes the credit by one month's payment. When the parties disagree about the date, compute the credit under each candidate date and present both. Counsel argues the date; the exhibit shows what it is worth.
The exhibit
A monthly table, from the earliest claimed separation date through the valuation date, with columns for principal, interest, taxes, insurance, offsets, and net. Below it, a short sensitivity strip: the credit under principal only, under full carrying costs, and under carrying costs less a use-and-occupancy offset. Counsel walks into mediation knowing the range, not just one side's number.