This is a California quirk tied to Proposition 13, and it catches new owners constantly. When a home sells, the county does not instantly reassess it to your purchase price. For a while, the regular (secured) tax bill still reflects the prior owner's lower assessed value. That is the bill your servicer sees and pays from escrow, even though your escrow was set up to collect at the new, higher amount. Later, the county catches up, reassesses to your price, and issues a supplemental tax bill covering the gap between the old and new amounts. The catch: that supplemental bill often never gets routed to your servicer. They never receive a copy, so it never gets paid, and it shows up as delinquent on county records while you assumed escrow was handling everything. The fix is straightforward: - Get a copy of the supplemental bill to your servicer directly and ask them to pay it from your escrow account, or confirm whether you are expected to pay it yourself. - Check your county tax collector's site after closing so a supplemental bill never slips past due.