Hey just wondering how VAT exemption works, so if i go up the north and buy a computer and show them my southern Vat number and business details and they don't add the vat, what do i do then, do i tell revenue in the south or will they even know i got the vat off something in the North??
No, you don't need to tell anyone what you've done. Keep the receipt as usual and file it; it will be VAT exempt, so you shouldn't claim any vat on it from the revenue. File it as normal in your year end accounts. I'm not an accountant, but this is what I've done with various items I've bought over the internet (both in Ireland and abroad) and my accountant is still speaking to me!
Getting the goods without VAT bring charged is not the end of the matter. One has to enter them in one's VAT records as "EU acquisitions" The entry goes in the outputs side and then , if one is entitled to an input credit for the VAT then one can claim that on the purchases or expenses side. The ultimate effect for allowable items is the two entries cancel out. However it is important to follow the procedure properly.