Erik Kabik/Retna Digital 1 / 7
Erik Kabik/Retna Digital 1 / 7

Heidi Montag says "irreconcilable differences" are the reason she's driving a stake through the heart of her marriage to Spencer Pratt.

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Montag filed for divorce in Santa Monica, Calif., Superior Court, says People.com. She sought legal separation from Pratt last May.

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"Heidi has amended her petition for separation and today has filed a petition for dissolution of marriage from Spencer Pratt," Montag's lawyer tells the site. "The couple has agreed they would like their divorce to be finalized in a timely manner in an out-of-court settlement. Both parties are amicable with each other and over the possibility of finalizing their divorce."

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The controversial reality couple officially tied the knot in Pasadena, Calif., in April 2009.