I have a foreign rental property that's been in service since 2011. I recently found out I could claim depreciation for it. I contacted a CPA and he said I would need to amend my forms from 2015 on since that's within the 3 year amendment period; he didn't mention anything about the missed depreciation prior to 2015. I did some research on my own and it seems like I can claim that depreciation as well since when I sell the property, the IRS is going to assume that I claimed it whether I actually did or not. However the form/procedure is quite confusing so I was wondering which of the below would be the better alternative:

1. Amend the 2015-2017 forms and either claim the missed depreciation from 2018 on or when I sell the property (assuming its allowed)? Or will I miss the opportunity to claim the missed depreciation because of rules around "changing accounting procedure" etc. (I went through the instructions but found them hard to follow)

2. Skip the amendments for previous years and file a form 3115 along with the 2018 tax form by the due date?