when do you have to pay VAT and excise?

if it's fedex/ups - you will get a letter in about 3 weeks, I usually don't mind that, after few months you get some letters from their debt collection agency, after the second I pay up why pay immediately for something you hate (import tax) immediately, let them wait

if it was sent per USPS EMS and customs wanted their cut then it would be delivered by sds who would want COD for the item. usually it slips undetected (if its small and <200$ declared value ) and delivered by an post

worst scum are gls/williames (they do usps airmail for items >4lbs) their handling fee is ridiculously high

no idea how it's handled by dhl, never used them from the states. Airbourne express (another courrier from us) do not deliver, they send you a letter and want you to call them to give them CC details or send a cheque, then they deliver.

I presume your shippment was fedex/ups - wait for the letter(s) - they don't tuck on much of a handling fee though.
lesson of the day - don't get anything delivered by courrier as you have to pay 21+4 % + handling fee on every item, if you send it by usps ems/airmail it usually does not cost you anything more, but I know sometimes courrier is your only option (had to do it myself recently for my skates, waiting for the first letter from fedex )