Qualifying status is determined at the outset of the policy if the contract meets certain criteria. Essentially, long term contracts (10+ years) tend to be qualifying policies and the proceeds are free from income tax and capital gains tax. Single premium contracts and those running for a short term are subject to income tax depending upon the marginal rate in the year a gain is made. All UK insurers pay a special rate of corporation tax on the profits from their life book; this is deemed as meeting the lower rate (20% in 2005-06) of liability for policyholders. Therefore, a policyholder who is a higher-rate taxpayer (40% in 2005-06), or becomes one through the transaction, must pay tax on the gain at the difference between the higher and the lower rate. This gain is reduced by applying a calculation called top-slicing based on the number of years the policy has been held. Although this is complicated, the taxation of life assurance-based investment contracts may be beneficial compared to alternative equity-based collective investment schemes (unit trusts, investment trusts and OEICs). One feature which especially favors investment bonds is the “5% cumulative allowance”—the ability to draw 5% of the original investment amount each policy year without being subject to any taxation on the amount withdrawn. If not used in one year, the 5% allowance can roll over into future years, subject to a maximum tax-deferred withdrawal of 100% of the premiums payable. The withdrawal is deemed by the HMRC (Her Majesty's Revenue and Customs) to be a payment of capital and therefore, the tax liability is deferred until maturity or surrender of the policy. This is an especially useful tax planning tool for higher rate taxpayers who expect to become basic rate taxpayers at some predictable point in the future, as at this point the deferred tax liability will not result in tax being due.