Economic theory stating stock market prices behave unpredictably due to the efficiency of the market.

Wasting asset

An asset which has a limited economic lifespan.

Wear and tear allowance

An allowance that is tax deductible for the cost of furniture and fittings provided in dwelling houses which are let out furnished.

White Knight

A company which comes to the aid of another facing a hostile takeover.

Windfall profits

A large profit resulting from an unusual or unexpected event.

Withholding tax

Tax deducted at source from earnings, such as dividends and interest. The purpose being to facilitate or accelerate collection.

Working capital

Capital used by an individual or company to fund the general day to day running of the business. Calculated as current assets (e.g. stock, debtors, cash) less current liabilities (e.g. trade creditors, bank overdraft).

Working life

Defined as the start of the tax year in which an individual reaches 16 years to the end of the tax year before reaching the prevailing state pension entitlement age.

Writing down allowance

See ‘capital allowances’.

Written down value

The cost of an asset, such as a car, after deducting amounts written off. For tax purposes it is the cost less capital allowances given to date.