HELP - Royal Mail - Customs Charge

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Hi all,

I'm getting married in October and ordered a custom veil off Etsy. The seller is based in Poland (I'm in Scotland).

Breakdown of cost for the veil is as follows:-

Item total £60.61
Delivery total £8.78
Subtotal £69.39
Tax £13.88
Order total £83.27

I've had a grey card through the door from Royal Mail stating a customs charge of £21.88 is due before they will release the item.

I messaged the seller to query this and her response was:

"I see that your parcel has arrived in the UK. Regarding the customs payment - we from our side attached the invoice with the indication "Vat collected" - unfortunately can not further affect the customs payments, in the UK with this can be unpredictable (often discuss it in the chat with other sellers) Try to send them your invoice from Etsy where it says that you have already paid the duty - this is the only thing I can help in this case.."

I'm trying to look online and i can't get my head round what is and isn't due on customs charges.

Does anyone have any advice? Or understand the whole custom charges thing because i am really confused.

I feel i'm being charged when i shouldn't be (have paid it meantime to get the veil anyway but aware i can claim it back if it's wrong).
 
It will be the VAT you are paying, which won't be much, but it's probably been pushed up by their "handling fee".