Is this because of brexit or was it always like this?
Not so much Brexit no, this was new EU rules that were being brought in and the UK adopted them into our own laws as part of Brexit and actually actioned them before the EU even got round to. I believe the EU have now implemented their version of it.
I think there is discussion thread on here about from a couple of years ago when the new rules started.
Basically anyone outside of the UK wanting to sell anything to someone in the UK, if the value of the goods is below £135 they need to be registered with HMRC and collect the VAT directly from the customer at the point of sale and then pay this to HMRC. Anything over £135 is handled in the same way as it used to be with the shipping company paying the import VAT/Duties and passing the bill with their charges on top to the customer.
They also took it as an opportunity to scrap the £16/£17 lower limit that we used to have before charging import tax/duties.
I remember there was a lot of companies that stopped selling to the UK as it wasnt worth the hassle to them having to register with HMRC and do all the paperwork to pay the VAT collected to them, big Market places like eBay and Aliexpress do all this for their sellers so they dont have to do it themselves.
No idea how its supposed to work with items below £135 with how they couriers know the VAT has been collected and paid, either just supposed to ignore anything under that value or if the seller needs to put something on the envelope to say the tax has been paid, pretty sure I have seen that second one on a few imported packages Ive had recently, but dont know if its mandatory.
There was a guy over on the pinballinfo forum recently having moan about a European company trying to charge vat on a small value order so he used another one and asked them not to include the VAT but he said they did, so will be interesting to see if he gets stung with import charges and a courier fee on top.
Also no idea how it works for private sellers with goods under £135 as they wont be collecting VAT on HMRCs behalf.