The new England and Welsh Rugby Union law, which will take effect in the 2019-20 season, means that England and Ireland will have to foot the bill for lawyers overseas.
The change comes into effect from January 1.
The new law, called the Rugby Law Reform Act, will force England and Scotland to pay an additional 3 per cent of their income in international law.
The increase will apply to both the English and Welsh national rugby unions and will be payable for two years.
The law will also affect professional clubs and individual players, as well as the professional bodies involved in player recruitment and training.
This means that any England or Wales player currently eligible to play overseas will be required to take the necessary training in order to qualify.
However, these players will not be eligible to be eligible for international duty until the end of 2019.
The law change comes after the Rugby Integrity Unit, the body that regulates international rugby, conducted a survey of professional players, coaches and others in 2015.
It found that more than a third of those surveyed said they would not consider taking up an overseas job as a result of the law change.
It also found that 40 per cent said they thought they would only consider it if the pay-off was worth the additional cost.
England and Wales were not the only European nations that have faced the financial impact of the Rugby Act.
Italy is set to be hit with a 2 per cent increase in its taxes in 2019.
In France, the increase will be 1 per cent.
Germany, where the new law is coming into force, has already implemented a similar increase to 1 per per cent over the next two years, and the UK is expected to follow suit in 2020.
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