On November 1, 2010, Sergeant Robert Martin was medically separated from active duty military service. Robert was entitled to and received $12,000 in severance pay.

His 2010 Form W-2 showed after-taxes income of $8,640 ($12,000 minus withheld taxes of $3,360). Robert filed his 2010 tax return in March 2011 and received a $567 refund.

Beginning in 2011, Robert received a service pension in the amount of $1,000 per month.

In August 2011, Robert received his VA determination letter, which showed he was entitled to a disability pension of 80% from the date of his discharge.

Does Robert need to file Form 1040X, Amended U.S. Individual Income Tax Return?