The drug regulator banned the antidepressant in under 18s in June 2003 but an investigation found GSK should have passed on data earlier.
Criminal charges cannot be brought because the laws on disclosure were not strong enough at the time.
GSThe Medicines and Healthcare products Regulatory Agency (MHRA) received data from clinical trials in May 2003 showing that patients under 18 had a higher risk of suicidal behaviour if they were treated with Seroxat than if they received a placebo.
Data also showed that Seroxat was not effective for treating depression in children and adolescents.
The drug was subsequently banned for use in under 18s. K has rejected claims it improperly withheld drug trial information.