The National Clearance Hub (NCH) may use the Customs Handling of Import and Export Freight (CHIEF) system to query an entry that was submitted. You should respond to this query through CHIEF, even if additional paperwork needs to be faxed to the NCH later. This will ensure that the NCH is aware that the query has been answered and should prevent any delays. There may be delays to clearance if you don't respond via CHIEF. Read more about UK's import and export processing system CHIEF.
If a query means that an entry needs changing, you must fax a copy of the amended entry to the NCH for clearance.