スルー取引とは、売上を水増しする為に、系列企業間で利ザヤを取ることなく転売する行為を意味します。

だから、Selling at the cost price with no profit margin to an affiliated company in order to boost the sales figure というような英訳になると思います。

連結会計が当然の国においては、意味の無い取引です。

The concept of a "pass-through transaction" does exist in English, in the field of accounting, taxation and securities.
It is a transaction where in practical terms, the incoming value equals the outgoing value, there is no profit/loss on the transaction. This could be for legitimate reasons, but it could be used for fraud or money-laundering as well.
See some examples here:
https://en.wikipedia.org/wiki/Payable-through_account
"Foreign financial institutions use PTAs, also known as "pass-through" or "pass-by" accounts, to provide their customers with access to the U.S. banking system. Some U.S. banks, Edge and agreement corporations, and U.S. branches and agencies of foreign financial institutions (collectively referred to as U.S. banks) offer these accounts as a service to foreign financial institutions. Law enforcement authorities have stated that the risk of money laundering and other illicit activities is higher in PTAs that are not adequately controlled."

https://news.navient.com/news-releases/news-release-details/...
"Navient issues its first student loan pass-through transaction of private education refinance loans"