Police can confirm Operation Cranmere, the investigation to identify anyone who may have supported Tom Phillips, has concluded.
It has not resulted in any charges.
Detective Superintendent Ross McKay says under the Solicitor General's Prosecution Guidelines, any prosecution is required to meet an evidential sufficiency test.
"In this case, based on current admissible evidence, that test has not been met and Police will not be filing any charges.
"We have always said that we believe Phillips was assisted by a small group of people at varying stages.
"Charges may be possible at a later date, if or when further information comes to light."
The Phillips family were notified of the outcome this week.
Police continue to support the government inquiry into the disappearance of the Phillips children.
It would not be appropriate to comment further while that process continues.
