*Originally Posted by ***Unregistered**:

I'm still a little confused and need clarification. Originally, I had an 1800 sq ft home. Now that I put on the 600 ft addition, I have a 2400 sq ft home. Although the kids used the whole 1800 sq ft at the beginning of the year, at the end of the year, once the addition was put on, the kids no longer have reign over the whole 1800 sq ft part of the home...they only use 1000 sq ft of the original home plus the 600 sq ft exclusive use addition. So, wouldn't my calculations look like this?

600/2400 = 25% exclusive use room

1000/2400 = 41.67% regular use space %

If we assume the time percent is 40%: 40% x 41.67% = 16.67%

16.67% + 25% = 41.67%

If you tell me your original calculation is the way it is supposed to be, I'll go with it. I like your 55% calculation better than my 41.67% calculation :-)

Thanks for your help, I really appreciate it!

There are no IRS guidelines for how to treat a room that is regularly used for only part of the year.

It sounds like you are saying that the 1800 square feet were used regularly for ten months. If so, then my calculation is correct (since you used it regularly for the majority of the year) and your calculation would be correct for 2015.