Should I write off part of the mortgage interest and how

[tdo061803]

My partner and I own an apartment together and share Airbnb’s profit/expense together. I understand the mortgage interest is deductible. Normally we would each deduct half of the mortgage interest and Turbotax does that correctly.

We rent out 2 rooms on Airbnb and that’s 40% of the apartment’s living space.

1. Do we each write off mortgage interest x 50% x 40%?
2. If 1 is correct, I have difficulty entering it in Turbotax. Turbotax gets 50% of the ownership and split the mortgage interest in half well. However, I couldn’t seem to find the place I can further calculate 40%. Does anyone have an idea how to do that?

Thank you!

[Hal_Al]

Do the math yourself and enter only the amount you want to deduct.

[tdo061803]

thank you @Hal_Al for helping me with my tax questions several times already.

Could you please confirm my formula is sound in the US? This is what I learned from the German regulation and need to know it's the same. I meant this formula

mortgage interest x % of ownership x % of rented living space

Another question: if I rent out part of the year, do I need to adapt the formula?

Thanks!

[Hal_Al · Accepted solution]

That's correct:  mortgage interest x % of ownership x % of rented living space.  You must have actually paid that much mortgage. 

Another question: if I rent out part of the year, do I need to adapt the formula?  Yes. For example if you rent it half the year; multiply by another 50%.