I have clients who are eligible to contribute to both a 457 plan and
the TSP for retirement. They believe they can put $12,000 in each tax
deferred. Is this correct?

Dear Watnik,

your client may make the total maximum contributions
(which may be more than the $12,000 if they are over
50, due to the catch up provisions) only once.
http://www.irs.gov/pub/irs-tege/457_outline.pdf
See limits on page 8 


Also, see page 7, third column, of IRS Publication 525
for the overall limits on deferrals.
http://www.irs.gov/pub/irs-pdf/p525.pdf

You'll find the specific limits for each year on 
Quicken's excellent summary page.
http://www.quicken.com/taxes/taxrelief/estimator/help/

Your client may split the total contribution among
as many retirement plans as they like, but the
TOTAL for the year can't exceed to legal limit. 

Wouldn't it be nice to be able to contribute that
maximum on each job? 

I looked into this a couple of years ago for my own
clients. I was also hoping they could fund plans
on two jobs. 

Best wishes,

Your TaxMama-ga

Great and quick. Thanks!!!