Tax Relief on annuity contributions

I understand that tax relief for payments to retirement annuity (in place pre 1988) is dealt with as a deduction from income, similar to personal allowance, but can someone confirm what the rule change in April 2006 was? I have read conflicting views on it, were the changes solely relating to the amount of contribution that can be made or is it that tax relief is no longer available on the same basis as referred to above?