Taxation on Renting House

Looking at renting a house I bought three years ago. The rent is only going to cover 60% of the actual mortgage so I'll be covering the other 40% from my own pocket.

I'm wondering though how do I declare the rent or what way does that work?
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Also, I'm getting mortgage interest relief as a first time buyer. Will I lose this because I am now renting?

I've also spent money on the house (e.g. insulation grant to cavity bead walls). Can this cost be offset against tax?

Any help would be greatly appreciated.

To save a lot of time ,first read/google Revenue.ie and study the "Revenue Guide to rental income IT70".

As regards expenditure prior to renting -no, cant be claimed.
First-time buyers interest relief -you'll lose this and you will pay much higher interest as a rented property , though some posters will argue that you don't have to tell your bank.

You are enteringa mine-field and really need to study everythihng from the tax position to all the nasty formalities of registering tenants -PRTB- etc.

read also the PRTB website and maybe Threshold website as well.

..after all this consider staying in the house and renting out the other rooms - this way you pay NO tax and have almost no paperwork.

It may be more profitable to get 4k a year from sharing your house than 8k p.a. renting out your house.(depedning on your tax base). Read about Rent-a-room scheme.

Staying in the house and renting out the rooms isn't an option because I have another house to go to.