Sept 11 (Reuters) - Financial advisor Cetera Financial Group has agreed to acquire all of the issued and outstanding equity of wealth management solutions provider Avantax in an all-cash transaction, valuing it at about $1.2 billion, including net debt, the companies said on Monday.

Shareholders of Avantax common stock will receive $26.00 in cash per share, representing a 30.3% premium from the closing price on September 8.

After the deal closure, Avantax will become a standalone business unit within the Cetera group, the statement added.

In June, investor Engine Capital LP had asked Avantax to explore strategic alternatives, including a possible sale.

(Reporting by Jaiveer Singh Shekhawat in Bengaluru; Editing by Krishna Chandra Eluri)