This blog post will explain you in a simple way how to scrap an asset under construction properly.
The costs are capitalized into the asset under construction via a posting into a project task.
These same postings would get settled into a Fixed Asset when the final settlement from the AuC to fixed asset is done.
You cannot scrap an Asset under Construction without settling cost to the final fixed asset because it will lead to errors during the execution of the settlement run (from Asset under Construction to Fixed Asset).
The proper way to scrap a Fixed Asset under Construction is by settling the cost to a proper Fixed Asset using settlement rules and settlement run.
Then you can scrap the final Fixed Asset to which the Asset under Construction got settled into.