You do not get a deduction. Repayments of a loan from a 401(k) or similar qualified retirement plan after a deemed distribution reported with code L (possibly along with code 1) in box 7 of the Form 1099-R become after-tax basis in your retirement plan. When you later receive distributions from the plan, a portion of each distribution will be a nontaxable distribution of the after tax-basis in proportion to the amount of after-tax basis in the account relative to the overall account balance.
