How to Calculate VRT rate on a vehicle conversion?

If the vehicle is currently register in Ireland then when the vehicle is converted the VRT due is the difference between the VRT rate on the vehicle prior to conversion and the new VRT rate on the converted vehicle.
Obviously if the vehicle was not previously registered (such as an import) then the full VRT rate must be paid.

Example:

1. Category B vehicle: VRT paid at 13.3% of OMSP upon registration.
2. Converted to Category A passenger vehicle of 14% and liable to VRT at rates of 14% based on CO2 emissions.
3. Credit to be given for VRT paid, but reduced in proportion to the reduction in OMSP

Worked Example

1. Registered January 2008 as Category B vehicle, OMSP of €17,456 at registration, VRT Paid €2,321
2. Converted to Category A passenger vehicle and Conversion declared March 2011
3. Category B OMSP = €8,350 (per Light Commercials Guide March 2011).
4. €8,350 = 47.83% of the original OMSP of €17,456.
5. VRT credit allowable is 47.83% of €2,321
6. Credit allowable is therefore €1,110.
7. Category A OMSP = €9,450
8. VRT chargeable at 14% (rate depends on CO2 emissions) = €1,323
9. Allow credit for residual Category B VRT of €1,110
10. VRT due on conversion = €213

Vehicle conversion, VRT Calculation Rules

• Where the conversion is from VRT Category D to EU Category M2, M3, N2, N3, T1-T5
  (VRT Category C), the additional VRT payable is € 200
• Where the conversion is from VRT Category D to EU Category N1 (VRT Category B) or
  EU Category M1 (VRT Category A), VRT is payable at the rate of the appropriate
  percentage of the OMSP of the converted vehicle, subject to specified minimum
  amounts
• Where the conversion is from EU Category M2, M3, N2, N3, T1-T5 (VRT Category C)
  to EU Category N1 (VRT Category B) or EU Category M1 (VRT Category A), the
  additional VRT is that payable at the appropriate percentage of the OMSP of the
  converted vehicle, subject to specified minimum amounts, less the amount of tax
  paid at the time of registration
• Where the conversion is from EU Category N1 (VRT Category B) to EU Category M1
  (VRT Category A), the additional VRT is that payable at the appropriate percentage of
  the OMSP of the converted vehicle, subject to specified minimum amounts less an
  amount calculated by applying the EU Category N1 (VRT Category B) rate to the
  current EU Category N1 (VRT Category B) OMSP of the vehicle, or less the EU
  Category N1 (VRT Category B) minimum amount as the case may be