stamp duty clawback

I am looking for some advice on stamp duty clawback. I was reading an question in the 'your money' section of the Irish Independent today which caused me concern. I bought an apartment in November 2001 and moved in as an owner occupier and as it was a new build I paid no stamp duty on the purchace price which was £151950 at the time. However due to unforseen events a few months later I had to relocate down the country and I rented the apartment out from February 2002. It remains rented out and I rented a private house down the country for the next 2 1/2 years. I have now bought a home and paid the relevant stamp duty but I continue to rent out the apartment in Dublin. I now realise that there will be a clawback of this stamp duty but I am unsure how to calculate it. I think the stamp duty for an investor in Nov 2001 was 9% and I am now very concerned that I may owe this amount plus the interest of .032% per day, which I estimate to be a total of around E20,000 in total. I would appreciate if somebody could clafify my position.

I now realise that there will be a clawback of this stamp duty but I am unsure how to calculate it

Under the clawback you will be liable for whatever rate of stamp duty an investor would have been liable for at the time that you purchased the property.