By Svea Herbst-Bayliss

NEW YORK, March 26 (Reuters) - Impactive Capital's board challenge at payment processing and information management services company WEX WEX.N may hit a speed bump after the company said this week the activist investor has not filed potentially critical paperwork.

The Federal Deposit Insurance Corporation and the Utah Department of Financial Institutions (UDFI) said Impactive may need to submit applications to press on with its proxy fight, but that it has not yet done so.

Impactive spent nearly a year laying the groundwork for what is shaping up as a closely watched and bitter board fight in which the hedge fund wants shareholders to kick out sitting directors and vote in four newcomers, including one of Impactive's co-founders, Lauren Taylor Wolfe.

New directors should help management focus on disciplined pricing, cost efficiency and simplifying the business to improve returns and unlock shareholder value, Impactive has said over the last year.

FAILURE TO FILE WOULD INVALIDATE PROXY VOTES: WEX

But WEX's filing, made on Tuesday and not previously reported, signaled there could be trouble ahead.

"Impactive's failure to file such applications with such bank regulators and obtain their prior approval could result in the invalidation of any voting of proxies obtained by Impactive for the annual meeting," the filing said.

Impactive owns roughly 5% of WEX and last month named the four director candidates it wants shareholders to elect.

A representative for Impactive said the hedge fund "will of course comply with all relevant regulatory requests made as part of the proxy contest process," adding, "As always, we are committed to enhancing value at WEX for all shareholders."

A representative for WEX declined to comment.

WEX, which has a market value of $5.3 billion, is primarily focused on fleet management, corporate payments, and employee benefits. Its board and management team have considered Impactive's input on strategy, capital allocation, and board composition, Reuters previously reported.

WEX owns and operates WEX Bank, a Utah-based industrial-chartered bank, and is therefore regulated by the FDIC and UDFI.

The company has not yet set a date for the 2026 annual meeting after last year's meeting was held in May.

For nearly a year, Impactive, run by Taylor Wolfe and Christian Asmar, has urged faster progress at WEX, including suggestions the company consider spinning off its benefits segment and adding an investor to the board.

WEX said in the filing that it tried to settle the standoff this month by proposing to add Impactive's two independent candidates. Impactive, the filing said, asked for a board seat for an Impactive principal and one of the independent candidates.