If there is no relationship between the two companies - the only link is that the employee works for both of them - then the employee can make salary deferral contributions up to an aggregate amount of $20,500, with no more than $13,000 to one of the SIMPLE IRAs.
The maximum aggregate contribution for an individual who reaches age 50 by the end of the year is $20,500. SIMPLE IRAs are subject to limitations established under IRC§ 402(g), which limits salary deferral contributions to $15,500 for 2007. Therefore, an individual who participates in multiple retirement plans can defer no more than $15,500 for 2007 (regardless of the number of plans in which he or she participates) plus catch-up contributions of $5,000.
On the other hand, if the two companies are affiliated or related in any way - if there is any one party that has ownership of both companies, whether in part or 100% ownership - or if there is any relationship that would constitute an affiliated service group, then the maximum amount that the individual can defer to both SIMPLEs may be limited to $13,000.
To learn more, check out the SIMPLE IRA tutorial.
This question was answered by Denise Appleby (Contact Denise)