Re-Importing Personal Property

I am returning to UK after 7 months abroad, cutting an expected longer stay short, so not eligible for ToR without a waiver (original planned contract was > 1 year, waiver has been asked for citing the contract). How does Returned Goods Relief work? As far as I can see returned personal property fall under the category. There's one line "If you are sending your items by freight, you should claim the relief by using customs procedure codes" - at what point will I have to do this?

Returned goods is requested at the time goods are imported. The procedure codes tell customs what type of import is being declared and therefore what duty treatment is required. The clearance agent should know what codes to use. Depending on how you are shipping you are likely to need to provide instructions on booking the shipping. You also need to provide proof of the original export thus proving the goods are returned.

Hi Rob Evans,
Customs procedure codes are entered by the declarant on the import declaration.
If you are using a customs agent/freight forwarder they should include that information for you.
Thank you.