How can I avoid duty when importing from USA to UK

[quizer]

I hope some one can help, I import health and beauty products from usa, sometime I get charged duty and sometimes I dont. Can someone help explain why this is the case? From what I can see USA shipper fills out all information same both times.

I am always charged vat, and there's no way of avoiding that as far I know.

Thanks

[agent006140]

is $35 the limit?
UK non profit organisation seems to be exempt?

[agent006140]

if the seller uses GPS,then you must have prepaid already