Supplementary Declarations (SDs) require similar information to a normal Single Administrative Document (SAD). However, for your Supplementary Declarations Procedure SDs you also need to state the date and time the Simplified Frontier Declaration was accepted. For the local clearance procedure you need to enter the date and time the entry was made in the local clearance record to release the goods and enter this information on the Local Clearance Procedure SD.
Classification and the Tariff
The Tariff is a key document when completing your SDs as it's the single source for all the classification you need.
As the SD is the document that allows HM Revenue & Customs (HMRC) to calculate the duty and taxes payable, you'll have to classify your goods to complete the SD, just as you would if you were entering a full SAD declaration at the frontier. Find out more about declarations and the Single Administrative Document.
However, because you're importing goods from outside the European Union, you'll need to use the 10-digit commodity codes. For more about commodity codes, see classification of goods.
You'll also need to use the Customs Procedure Code (CPC) to identify the nature and movement of the goods to ensure the correct duties and taxes are applied.
You can find a listing of CPCs in Volume 3 of the paper Tariff or online (subscription required).
Read more about how to use the UK Trade Tariff.