You have to get the land valued at 6/4/74 most auctioneers i think can do this. The inflation /indexation multiplier from 1974/75 to date is 7.528.
Disposal Consideration 300,000
Less Selling costs say 10,000 (Planning Legal & Auctioneers etc)
____________________290,000
Deduct
Value adjusted for inflation at 6/4/74 say £1,000 (€1,270) apply multiplier of 7.528 which equates to €9,561.
Water Connection charges 300 - Is this euro or pounds (when) apply multiplier
Solicitor 500, Is this euro or pounds (when) seems high adjust for inflation prior to 6/4/74 and apply multiplier
Deduct Allowance 1,270
Tax * 20%
Can't work out the exact figures but the above info will help you calculate.
See
here specifically chapter 11 1. Sale of an investment property and appendix 1 for inflation /indexation multiplier figures.