I'm sure this is a fairly easy question, but I don't work with SIMPLE plans and I want to be sure I give an accurate answer...
Client is terminating his SIMPLE Plan as of 12/31/2004 and starting a 401(k) as of 01/01/2005. There will be "receivable" contributions from December payroll that actually go into the SIMPLE Plan in January. Is this an issue with the SIMPLE exclusive plan rule? It doesn't seem as though it would/should be in practice, but then I got thinking .................any help is appreciated.

No, it's not an issue, doesn't violate any rules.