If I am on the managing board of a company which declares bankruptcy, will it affect my personal credit rating?
I am particularly interested in Western Australia.
The answer to your question is governed by the structure of the company and your ownership or lack thereof in the business. Australian business can be structured the same way U.S. ones are, as a sole proprietorship, partnership, LLC, or company. If you are only on the board and have no equity, you cannot be affected. You must have some amount of equity in the business to have any chance of being affected.
If the business is a sole proprietorship, then the single individual running the business is personally responsible for all debt and the inability to pay obligations would result in personal bankruptcy which would in all likelihood affect your credit score (it would in the U.S.).
If it is a partnership, then anyone holding stock in the company is likewise personally responsible for a portion of the debt, and can be subject to bankruptcy and credit score implications.
If the business is structured as a limited liability company or a corporation, a stakeholder's personal finances are separate from the business's and their credit score cannot be affected.