From Connecticut Sports Law Blog
"A signing bonus is compensation earned by joining a team, but it is frequently paid out over time. For example, let’s say that Jim is an in-demand pitcher. On January 1, 2009 he signs with a team that offers him a $10 million signing bonus to be paid over a five year contract term. Without making sure that the bonus fits within an exception in the 409A regulations, Jim would be receiving non-qualified deferred compensation subject to 409A. That means that Jim would have to pay taxes on $10 million of income in 2009 and be subject to a 20% excise tax on top of that. The result? Jim is only paid the $2 million due for the first year’s payment, and already owes the IRS $2 million in excise tax plus income taxes of approximately $3 million."