Depreciation Value Source

[Gabe C.]

I'm working through some tax prep, and was trying to get to a depreciation value to use on secondary that I converted to a rental. The value assessed by the county is easy to find/use, but my property is worth more than the most recent assessment, and I feel like I might be leaving some money on the table if I use it. I remember reading that I could use my appraisal from the time of purchase, but I just went through the appraisal, and it doesn't separate the value of the land/property the way I need it.

Should I just use the value on the tax assessor site, or is there another way? Are there any rule of thumb formulas like 30/70 that the IRS will accept? The difference in value is only about 3% (divided by 27.5), so maybe it's not worth quibbling over...