American citizens with businesses outside the country now have a new tax to think about. Known as the “transition tax,” it went to effect at the end of 2017, and will need to be considered for the 2018 fiscal year.

The tax requires businesses to pay 15.5% on foreign earnings held in cash and equivalents, and 8% on other earnings. It applies to shareholders of foreign corporations and includes American owners of small businesses which are based abroad.

The idea of the tax is to “repatriate” or bring back, money that these businesses maintain outside the US. The tax will apply to the company’s accumulated earnings and profits starting in 1986 until the end of 2017.

Although large corporations will have to pay the taxes on cash held in foreign countries, they will also be able to take advantage of the 100% dividends received deduction. This means that they can repatriate their dividends and will not have to pay any taxes.

Small businesses owned by US citizens will have a harder time of it. A small businesses cash flow is constrained by the transition tax. Also, they need to deal with the increase in complexity of the tax system in general.

“Getting clients to understand the law is the first battle, getting them to believe you is the second battle,” said Richard Tannenbaum, a CPA and leader of the global mobility practice at Mazars USA.