The Serious Fraud Office (SFO) has charged Barclays Bank PLC with "unlawful financial assistance" related to billions of pounds raised from Qatar in 2008.
The same charges were bought against Barclays PLC in June last year.
The move to charge Barclays Bank as well is significant because it holds the banking licence that allows it to operate in different countries.
So, if Barclays was found guilty, it could lose that crucial licence.
In 2008, to avoid a government bailout, Barclays took a £12bn loan from Qatar Holdings, which is owned by the state of Qatar.
Under that deal Barclays loaned £2.3bn back to Qatar Holdings.
The SFO alleges that loan was used either directly, or indirectly, to buy shares in Barclays, which the SFO says is "unlawful financial assistance".
In response, Barclays said: "Barclays PLC and Barclays Bank PLC intend to defend the respective charges brought against them.
"Barclays does not expect there to be an impact on its ability to serve its customers and clients as a consequence of the charge having been brought."
Other than the charge, the SFO has released very little information about its investigation.
But a top lawyer said the case is likely to revolve around whether the directors knew what the loan was being used for.
"The SFO may have to establish the precise intention of the directors when making the loan which is the subject of the investigation and it might be difficult to prove to a criminal standard that they had an unlawful intention," said Philip Marshall QC at Serle Court Chambers.