In the US, is all interest deductible? And since your taxes are spread across federal/state/municipal, is it deductible from the tax basis (don't know what the exact term is - the amount your net taxes are calculated on) for all of them?
Interest is deductible in various situations, but for typical filers only interest on their primary residence is deductible.
This is the case for federal taxes. State stuff is all over the map; I don't believe mortgage interest has been deductible in any of the states I've paid taxes in (MD, MA, CA, IL) but there may be some where it is. For the most part there are no municipal or county-level income taxes, so the whole issue is moot for those jurisdictions.
