Form 4562 uses the amount of depreciation my rental could claim over the life of the rental. This was then used to calculate that cost basis when I sold it instead of using the actual cost of property less land. Is this correct or a glitch in the software?
This is the correct calculation of basis. Your original purchase cost (including land), plus closing costs, and improvements, less any depreciation taken over the life of the asset equals the adjusted basis for the sale.
However, land should not be included the calculation for depreciation. You may wish to review your entries to be sure you entered only the cost of the rental home plus closing costs plus improvements. If the number you entered included the cost of the land, you must enter the land portion in the box provided for that amount.