Was the $19,000 a Roth contribution to the individual 401(k)? If so, that uses up the entire employee regular contribution limit and is not deductible. If so, only the employer contribution, which must be made to the traditional 401(k) account, is deductible.
To see the calculation, examine the Keogh, SEP and SIMPLE Contribution Worksheet in TurboTax. This TurboTax worksheet implements the Deduction Worksheet for Self-Employed from Chapter 5 of IRS Pub 560.
