http://en.wikipedia.org/wiki/Withholding_tax

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Note added at 22 mins (2008-02-29 18:25:15 GMT)
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Domestic withholding tax is also applied to interest and/or dividend payments, typically at standard rate and paid directly to the Revenue authorities. This secures immediate payment of at least a substantial proportion of the tax due. Individuals whose total income does not exceed the higher rate tax threshold need not then complete a tax return (jurisdiction dependent).

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Note added at 23 mins (2008-02-29 18:25:47 GMT)
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Dividend taxation

A minimum rate of tax may be deducted at source from dividend payments, in addition to Corporation tax. In the USA, this is still seen as controversial. In the United Kingdom, tax is not withheld at source, but the recipient is given a "tax credit" on the dividend statement, which has the effect that a basic-rate taxpayer has no more tax to pay: higher-rate tax-payers have further tax to pay. The tax credit once represented advance corporation tax paid by the company, but since 1999 this is no longer the case.

The position that arises if the share-holder is not resident in the country concerned is complicated. The country where the dividend is paid may withhold tax and simply retain it, or it may permit payment gross but inform the tax authorities in the country of residence (though not in the case of tax havens). A double taxation treaty can partially or fully prevent a single gain giving rise to a tax liability in two different jurisdictions.

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Note added at 36 mins (2008-02-29 18:39:10 GMT)
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i forgot:

http://www.google.com/search?hl=en&q="accrued withholding ta...