Can i not depreciate capital improvements made last year on a rental but add to basis when i sell this year? house has been up for sale since fall last year...

No, you can not depreciate capital improvements made on your rental.  The amount of the capital improvements are added to the adjusted cost basis for your rental.  When you sell the rental you will use the adjusted cost basis to calculate any gain or loss you may have on the sale.

so do i not report the capital improvements at all on my 2018 taxes but add them to my 2019 taxes in determining the basis of the property?

The capital improvements are not added to your tax returns, they are added to your adjusted cost basis  records for your property and when you sell the property then you report the adl cost basis  when you input the sale information

thanks...

You are welcome !