Capital Acquisitions Tax calculation with different thresholds?

[Savonarola]

Can someone please explain how the CAT thresholds work? For example, is the following calculation correct for a Group A situation? (ignoring the €3k annual exemption)

Date of gift **Amount**Cumulative**CAT threshold**Taxable**Tax rate**Tax payable
01/01/12 **** 200k **** 200k **** 250k ******* nil ****** 30% ***** nil
01/01/15 **** 100k **** 300k **** 225k ****** 75k ****** 33% ***** 25k
01/01/16 **** 100k **** 400k **** 280k ****** 120k ***** 33% ***** 40k – 25k = 15k

I think it is clear that no tax is payable on the 2012 gift. The additional gift of €100k in 2015 makes the cumulative exceed the (reduced) threshold by €75k. Is the 75K taxable at 33%, even though the rate at the time of the gift was only 30%?
Moving on to the present/near future; with an additional gift of €100k, is the cumulative amount (€400k) taxed at the current rate (€120k x 33%) less the tax already paid?
Or have I got it completely wrong?

And what would happen if the thresholds were lowered again? Would a gift that is currently not taxed become liable, e.g. a gift made today of €275k is not taxed, but if the threshold were lowered next year to €250k would tax become due on the €25k excess?
Any enlightenment gratefully received!

 

[jpd]

The calculations are as follows for 2015 and 2016

2015

1) Calculate the total tax on the cumulative amount at current rates
Cumul value = 300k - threshold 225k = 75k taxable x 33% = 25k

2) Calculate the total tax on the cumulative amount minus the amount in 2015 at current rates
Cumul value = (300k -100k) or 200k - 225k = 0 so tax due = 0

Subtract 2) from 1) to get the tax due or 25k - 0 = 25k

2016

1) 400k - 280k = 120k x 33% = 40k
2) 400k - 100k = 300k - 280k = 20k x 33% = 6.7k
Tax due = 40k - 6.7k = 33.3k (effectively all of the 100k is taxable @ 33%)

It's not less the tax already paid - it's less the tax that would have been paid under the current rules which could be quite different. Effectively, they only tax the new amount at the current rates

 

[Savonarola]

Many thanks JPD
Clearly I was barking up the optimistically wrong tree!