Claiming interest as expense on rental income

Hello,
I'm wondering if entire interest is claimable on rental income.
eg. If monthly rent is say 850 euro, and monthly mortgage interest is 750 euro; does this mean that monthly taxable income would be 100 euro? (leaving other claimables such as insurance, wear and tear etc. aside).

Cheers.

Provided all of the mortgage amount was used to purchase/renovate/kit out the rental property, and you are registered with the tenancy board, then yes, the interest if fully deductible.