Looking on the internet deeply has found these results:

as per clarification is the most popular phrase on the web.

as per clarifying 160 results on the web	as per clarification 18,100 results on the web More popular!
Some examples and use cases from the internet:	Some examples and use cases from the internet:
As per the note from your mother. All postal orders, ma'am, are dispatched daily, as per headquarters commandments, as per I always do. Bail granted, subject to conditions as per application. The Honourable Miss Fisher's laundry, as per usual. The accounts were separated as per Italian legal provisions. It was videotaped as per prison policy. Detective Amaro followed procedure as per his delegate. Luminance values shall be measured as per Section 6.2.	Luminance values shall be measured as per Section 6.2. Bail granted, subject to conditions as per application. It was videotaped as per prison policy. All postal orders, ma'am, are dispatched daily, as per headquarters commandments, as per I always do. As per the note from your mother. Detective Amaro followed procedure as per his delegate. The accounts were separated as per Italian legal provisions. The Honourable Miss Fisher's laundry, as per usual.

as per clarifying

160 results on the web

as per clarification

18,100 results on the web

More popular!

As per the note from your mother.
All postal orders, ma'am, are dispatched daily, as per headquarters commandments, as per I always do.
Bail granted, subject to conditions as per application.
The Honourable Miss Fisher's laundry, as per usual.
The accounts were separated as per Italian legal provisions.
It was videotaped as per prison policy.
Detective Amaro followed procedure as per his delegate.
Luminance values shall be measured as per Section 6.2.

Luminance values shall be measured as per Section 6.2.
Bail granted, subject to conditions as per application.
It was videotaped as per prison policy.
All postal orders, ma'am, are dispatched daily, as per headquarters commandments, as per I always do.
As per the note from your mother.
Detective Amaro followed procedure as per his delegate.
The accounts were separated as per Italian legal provisions.
The Honourable Miss Fisher's laundry, as per usual.