
Section 163(h) Mortgage Interest Deduction in 2026: $750K Cap, Grandfathered Loans, and HELOC Rules
Section 163(h) decides whether your largest Schedule A line is a $14,000 deduction or an $8,500 one. Here is how the permanent $750,000 TCJA cap, the grandfathered $1 million pre-2018 loans, the HELOC "substantial improvement" rule, and the 2026 return of the mortgage insurance premium deduction actually work — with worked examples and the records you need on audit.










