You will need to start some inheritance tax planning if you have a large estate.

The tax is paid if the value of your estate is worth more than the "chargeable transfers" limits. 

Any assets you have transferred to someone else in the last 7 years before death are included in this calculation.

Chargeable Transfers
Death Rate
%
Lifetime Rate
%
2008/09
£’000
2007/08
£’000
Nil
Nil
0 - 312*
0 - 300*
40
20
Over 312*
Over 300 *
*Potentially increased for surviving spouses or civil partners who die on or after 9 October 2007.

Reliefs:
Annual exemption £3,000 Marriage - parent £5,000
Small gifts £250   - grandparent £2,500
  - bride/groom £2,500
  - other £1,000

Reduced charge on gifts within seven years of death:
Years before death
0-3
3-4
4-5
5-6
6-7
% of death charge
100
80
60
40
20