The US securities regulator is pushing more companies to disclose how much cash they hold offshore, as attention focuses on the impact of tax rules that encourage US companies to keep earnings overseas.

The Securities and Exchanges Commission has asked companies including Dow Chemical, Fortune Brands, Caterpillar and CIT to increase the information they provide to investors about overseas earnings and cash.

Currently there is no firm rule about whether companies should disclose details of how much they hold overseas. However, the SEC typically raises questions through its public comment letters when it believes further information may be relevant and material to understanding a company’s liquidity. The letters are part of routine disclosure reviews of companies’ filings and are separate from the regulator’s enforcement activities.