They are probably referring to the $10k salt limit this is the total deductible state and local tax and interest deduction. In any big city your property taxes

They are probably referring to the $10k salt limit this is the total deductible state and local tax and interest deduction. In any big city your property taxes are probably 5k+, add state taxes, you don't have any room under the 10k limit to deduct mortgage interest. That deliberate Republican property tax screw you change made a big difference (the old deduction was also a huge tax deduction for huger middle class to wealthy people).