Australia risks driving investment offshore if it imposes a proposed five per cent tax on large companies, the chair of one of the nation's largest retailers declared.

Massive employer Wesfarmers, which runs Bunnings, Kmart, Target and Officeworks, is holding its annual general meeting at 4pm on Thursday where its chairman Michael Chaney will lament large taxes imposed on big companies.

He will reference a proposal by the Productivity Commission to slap a five per cent cash flow tax on large companies.

This tax would strictly apply to cash, rather than profits, and would allow businesses to deduct the full cost of capital investment against the tax.

It would also lower the corporate tax rate for businesses with revenue between $50m and $1b from 25 to 20 per cent.

Wesfarmers currently

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