June 26 (Reuters) - Zalando is being investigated by Germany's financial watchdog over its 2025 financial statements, the regulator said on Friday, adding it had concrete evidence the online fashion retailer breached accounting regulations.

Shares in Berlin-based Zalando fell 6% by 0824 GMT, wiping out a 5% gain since the start of this year.

The regulator, BaFin, said that information regarding a transaction with a related party in connection with Zalando's acquisition of About You may have been incorrectly omitted from the notes to the financial statements.

Zalando said in a statement that it was in close and constructive dialogue with BaFin on the matter.

"We confirm that we have received information regarding the initiation of a review of our 2025 financial statements by the federal financial supervisory authority," the company said.

"According to Zalando SE's assessment, this is a purely formal and materially insignificant aspect of the notes to the financial statements," it said, adding all relevant information regarding the acquisition of About You was already fully publicly accessible as part of the public tender offer.

Zalando concluded its acquisition of About You last year, in a deal valuing its smaller rival at 1.13 billion euros ($1.29 billion).

"At first glance, this seems more like a technical glitch," a trader told Reuters. "There is some uncertainty, but it doesn't seem to be that serious."

($1 = 0.8791 euros)

(Reporting by Linda Pasquini and Daniela Pegna; editing by Thomas Derpinghaus, Thomas Seythal and Susan Fenton)

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