Here's our quick summary to everything you need to do to ensure your business is Brexit ready and your clients are able to still receive the amazing service they expect from your business.
You will not be able to buy goods from or sell goods to the EU without an Economic Operator Registration and Identification (EORI) number. Get an EORI number that starts with GB to move your goods into or out of the EU
You may not be able to trade goods with the EU if you do not get your business ready. It may be an helpful to get an agent to support you with the declarations, for more information about this please follow this link. Decide whether to get an agent or make declarations yourself
When moving goods between or though EU countries and common transit countries you can use the Common Transit Convention (CTC). This will allow you to; move your good quicker because customs declarations are not required at each border crossing, only pay customs duties when the goods reach their final destination, complete some customs procedures away from the border. To do this you'll need an EORI number and need to register for the New Computerised Transit System to make transit declarations. Register for a quicker way to move your goods to the EU. This is applicable when moving goods under Community Transit - the trader must submit Community Transit declarations electronically. For more information please follow this link https://www.gov.uk/guidance/using-the-new-computerised-transit-system-to-move-goods-across-the-eu-and-efta-countries#how-to-register-for-and-use-ncts-online
When exporting goods you will need a guarantee in place to cover customs or import VAT duties while your goods are being moved. Your guarantee can be; a customs comprehensive guarantee if you move goods under transit more than 3 times a year or an individual guarantee for single movements, 3 times a year or less
You may not be able to transport goods through or between EU countries without an ECMT permit.
A final few things to note
You can set up a Duty Deferment Account (one monthly payment of customs duties if you import regularly)
You will need to check if there are any procedural changes for importing goods they, ie. change in labelling of goods, apply for licences
Here is an online assistance checker to help you https://www.gov.uk/prepare-business-uk-leaving-eu
Please also have a look at the Simple Trader Checklist for further support.