Investors & landlords

To make it simple, I suggest you use your home office on only one rental activity. It would get quite complicated to try to enter the actual asset under several different properties and it's not necessary.  

Also, it's quite likely it will be much easier for the long term if you allocate the expenses yourself.  Even though you are taking into consideration all rentals, your home office square feet is actually the same so the business use percentage would be office square feet divided by the total square fee of the home.

Be sure to separate out the land portion of the home.  You can use the city or county tax assessment records to figure out home versus land value.  When you enter the home asset for depreciation, be sure to enter only the business use percentage of the cost (when a personal use asset, like your home as example, is converted to business use, then the actual cost basis is the lesser of fair market value (FMV) on the date of conversion or the actual cost).  For a home, most commonly, the cost is lower than the FMV.

De Minimis Safe Harbor Election (mentioned by Carl here are the details)

This election for items $2,500 or less is called the De Minimis Safe Harbor Election. This election is an option you can take each year that lets you write off/deduct items $2,500 or less as expenses instead of assets. Expenses typically reduce your income by a larger amount than depreciating an asset over multiple years does. This means you could get a bigger refund.

If you decide to take this option, a form called De Minimis Safe Harbor Election will show up in your tax return. This election will apply to all your businesses, rental properties or farms.

Here are the rules you need to meet to take this election:

• You don't have an applicable financial statement (most people don't).
• You have a consistent process for how you record expenses and assets.
• You record these items as expenses on your books/records.
• The cost of each item as shown on your receipt is $2,500 or less.
• Rental Property select Edit > Other expenses > Other Miscellaneous Expenses
• Enter Description (Safe Harbor ...) and amount (not entered as assets under this election)

@Tootaxy