1 In 2015, 100% of net adjusted business profits income up to the maximum of $18,000 or $24,000 if age 50 or older can be contributed in salary deferrals into an Individual 401k (2014 limits are $17,500 and $23,000 if age 50 or older). 2  Profit Sharing Contribution.ndividual 401k contribution calculation for an S or C corporation or an LLC taxed as a corporation. 1  Salary Deferral Contribution. 2  In 2015,100% of W-2 earnings up to the maximum of $18,000 or $24,000 if age 50 or older can be contributed to an Individual 401k (2014 limits are $17,500 and $23,000 if age 50 or older).