Multinational infrastructure and property trusts could be disproportionately affected by planned changes in business tax rules, according to law firm Minter Ellison.

The federal government has indicated the proposed reduction in company income tax rates from 30 per cent now to 28 per cent in 2014/15 would have to be partly paid for by stricter requirements under the thin capitalisation rules.

But the proposed changes could also affect trusts, which would not benefit from a lower company tax rate.

"It is the case that there are large groups, like infrastructure funds and property funds, which are subject to thin capitalisation, but they are not going to benefit from the reduction in the company tax rate, because they don't pay company tax," Minter Ellison partner Karen Payne said at a presentation yesterday.

"A stapled group will have a company and a trust, but it could be that the thin capitalisation rule is going to impact the trust as equally as it applies to the company side of the stapled [group], because the rules don't distinguish that you are paying company tax."

The thin capitalisation rules apply to Australian entities investing overseas and foreign entities investing in Australia and were put in place to prevent companies from shifting profits to countries with lower taxes.

The proposed changes will affect the level of gearing a company is allowed to have, reducing the debt-to-equity ratio requirements from 3:1 to 1.5:1.

"That is clearly going to affect companies in terms of their borrowings, and a consequence of that is that groups will have to go back to the market to refinance their debt and/or equity, so that they are within those thin capitalisation limits," Payne said.