If you buy anything from overseas you may get charged VAT (with a percentage that can vary dependent on the country of the supplier).
If you are not VAT registered you will have to pay the VAT.
To avoid this, first of all, speak to the supplier and see if they can take VAT off.
If they agree, great. If they don’t agree, they may take the VAT off if you become VAT registered i.e. you can give them a UK VAT number.
All you now need to do is become VAT registered. However, you don’t need to VAT register usually until you get to £82,000 turnover so check that it will not adversely affect your customers i.e. if they are not VAT registered, they will not be able claim back the VAT that you will charge.