You should be subject to tax on any rental income less 75% of mortgage interest, capital allowances on fixtures and fittings, repairs, service charges, PRTB charges, management fees and accountancy fees.
The above list isn't exhaustive.
There's also the NPPR charge to pay which isn't deductible per Revenue.
In order to claim a deduction for interest on the mortgage, the tenancy must be PRTB compliant.
Only interest arising on a loan for the purchase or improvement of the property is deductible.
The fact that you're not making a profit on the deal isn't sufficient...you may be including the capital element of your mortgage repayments or 100% of the interest or expenses that aren't deductible.
Hope this helps.
Any questions, feel free to post or PM me.
Regards
Gordon