A CN22 customs declaration form, also known as a Customs Declaration or Dispatch Note, is used for international shipments of goods with a value below a certain threshold (currently £270). Custom forms are mandatory for all gifts and goods sent outside the UK from England, Scotland or Wales. If posting from Northern Ireland, they're only needed for non-EU destinations, except the UK. This form provides customs authorities with information about the contents of the package, its value, and other relevant details.

Here's a step-by-step guide on how to complete a CN22 customs form:

CN22 forms are freely available at your local Post Office. You can also download them online with Royal Mail. You should complete the CN22 legibly in BLOCK CAPITALS.

1. Sender's name and address – include your full name and address including postcode
2. Content type and description of contents – include an accurate description of each item enclosed. This will help to avoid delays or customs officials needing to open your item
3. Value, quantity and weight of each item
4. Total quantity – add the total number of items within your package
5. Total weight– this is the total weight of your item. If you don’t know and can’t easily find out, weigh your package and complete in your local Post Office branch
6. Total value – this is the total value of all the items in the package. Write the value in British Pounds (GBP)
7. HS tariff number – is mandatory for businesses only – you need to provide the HS tariff code which you can find at GOV.UK 
8. VAT reg number / EORI number – are mandatory for businesses only – if your business has both, please use the EORI number
9. Signature and date are mandatory – you must physically sign and date the customs forms on the day you post the item

Remember that customs regulations can vary between countries, and some items may be subject to specific restrictions or duties. It's essential to research the customs requirements of both the UK and the destination country before sending an international shipment. If you have any doubts or questions, consider consulting with your local customs office or postal service for guidance.