Solo 401k Catch-up contributions
All 401ks including solo 401k allow for those age 50 or over by the end of the calendar year to make catch-up contributions on top of employee and employer contributions discussed above. For tax/plan year 2012, the catch-up contribution limit is $5,500, which can be applied as a Roth Solo 401k contribution or regular (pretax) contribution. Further, since catch-up contributions are a sub category of elective deferrals, they are added to the annual deferral limit which is $17,000 for 2012, thus resulting in a total salary deferral of $22,500 for 2012 when including the catch-up amount. By the way, this entire amount can be treated as a Roth Solo 401k contribution.