Hi Guys,
I work in the motor trade so I'm reasonably up to speed on this!
There are a few issues here so I'll try to shed some light!
VRT
There are no changes to VRT on bikes that I'm aware of - the existing cc based system remains. There are far reaching changes to VRT on cars however as introduced in the last budget. The number of bands has been increased to 20 and the range is now from 7% to 37% of the open market selling price (OMSP). This is a value set by Revenue and NOT the price you pay for it.
I won't bore you all with the implications of these changes for passenger cars as this is a bike forum, but suffice to say that larger, especially automatic and diesel vehicles are getting hammered. As an example a 2017 Vovlo XC90 I have will see an increase in VRT of approx €4,000!!
Tariffs
Yet to be clarified but will depend on the outcome of the "deal or no deal" negotiations!
In the event of no deal being agreed the World Trade Organisation tarrifs will apply to all imports into ROI after January 1st 2021. I haven't looked up the rate on bikes but I'm assuming it's 10% as with cars.
If our political buddies agree on a deal then this will almost certainly not apply.
VAT
This is the show stopper!
Post January 1st 2021, all vehicles imported from Great Britain will have VAT applied to the purchase price. This will obviously increase the cost of the vehicle \ bike by 21%. My understanding is that this will not apply to imports from Northern Ireland where the vehicle was in the North prior to January 1st 2021. However, any vehicle taken from Mainland GB to Northern Ireland post January 1st and subsequently imported into ROI will have VAT applied to it.
As an aside, anyone who currently has a UK registered vehicle in ROI would need to get it registered quickly! If you don't then the new rates of VRT will apply from January irrespective of whether you can prove you bought it prior to then. If you can't prove you imported it prior to January 1st 2021 (you'll need an invoice and a shipping docket) then the dreaded VAT and possibly a tariff will apply.
Hope that helps! The bottom line is that pretty much everything will get dearer to import - by how much depends on what it is and ultimately what happens with Brexit negotiations.