Beta This part of GOV.UK is being rebuilt – find out what beta means

HMRC internal manual

Customs Special Procedures Manual

Bicycle parts: completion of End-use relief

Under Article 14c, End-use is considered complete at the end of the calendar month. Therefore you should monitor your importations, so as to ensure that you do not exceed the 299 units per month limit on the essential bicycle parts, otherwise ADD becomes due on the value of the excess  quantity imported in that calendar month.