The UK has a similar VAT scheme in place as the EU. Except without strange and confusing acronyms. The UK VAT scheme for Low-Value Consignments allows for simplified importation and collection of VAT due at checkout of below 135£. Anything above that means full customs procedure and duties. The registration is not quite as efficient as IOSS registration in some EU countries, it can take up to 8 weeks. The scheme is called UK VAT. We love it.
To make sure you are providing a good customer experience, we recommend taking advantage of these schemes always when possible. That means lower shipping costs and faster delivery. And, most importantly there are no post-sale actions required from the end customer which directly reduces returns significantly.
Going above the threshold, customs procedures are normal. For the above threshold shipments, you should find a reliable and capable logistics partner and set up a Delivery Duty Paid (DDP) delivery method. DDP removes the requirement for you to be registered for VAT / IOSS as the VAT is collected at customs. DDP is, as you probably guessed, much more expensive.
Unlike IOSS, reporting and payment of VAT are done quarterly. Failure to do so can put an end to your business. Your existing accountant should be capable of handling the limited accounting requirements on the cost side. If you are only selling, not buying, and paying VAT, you will get the full data set from EAS Dashboard and it should be delivered to the company managing your VAT.
Companies from some countries may require a fiscal representative to be present. They are jointly and separately liable for the seller's taxes, making the role costly. Countries NOT requiring fiscal representatives are the usual suspects: Switzerland, Norway, the US, Canada, Australia, New Zealand, and all EU countries.
You can perform the registration yourself, it is really not complicated: https://www.access.service.gov.uk/login/signin/creds. You can find our instructions here.
You can also file VAT by using a tax agent such as EAS.