This excerpt taken from the WPPGY 20-F filed May 12, 2009.
Backup withholding and information reporting
Payments of dividends and other proceeds with respect to ordinary shares or ADSs by a US paying agent or other US intermediary will be reported to the IRS and to the US Holder unless the holder is a corporation or otherwise establishes a basis for exemption. Backup withholding may apply to reportable payments if the US Holder fails to provide an accurate taxpayer identification number or certification of exempt status or fails to report all interest and dividends required to be shown on its US federal income tax returns. Any backup withholding tax will be refunded or allowed as a credit against the US Holders US federal income tax liability if the US Holder timely gives the appropriate information to the IRS. US Holders should consult their tax advisers as to their qualification for exemption from backup withholding and the procedure for obtaining an exemption.