The retirement system may accept as payment for repurchase of relinquished creditable service under section 79-921 or purchases of service credit made pursuant to the School Employees Retirement Act a direct trustee-to-trustee transfer from (1) an eligible tax-sheltered annuity plan as described in section 403(b) of the Internal Revenue Code or (2) an eligible deferred compensation plan as described in section 457(b) of the code on behalf of a member who is making payments for such relinquished creditable service or service credit. The amount transferred shall not exceed the amount of payment required for the relinquished creditable service being repurchased or service credit being purchased, and the repurchase of such relinquished creditable service or the purchase of such service credit shall qualify as a purchase of permissive service credit by the member as defined in section 415 of the code.