The elections watchdog is appointing an independent international expert to examine the chaos surrounding the Holyrood count.
More than 140,000 ballots were rejected across Scotland
BBC Scotland understands that the Electoral Commission took the decision at a meeting in London on Thursday.
The commission is already conducting its own review.
However, it has been under pressure to involve outside expertise because of its role in overseeing the arrangements for the Scottish Parliament poll.
Technical failures, confusion about how to fill in ballot papers and problems with postal votes were all blamed for the problems which beset last week's poll.
Figures obtained by the BBC found that more than 140,000 votes were rejected, the majority on the constituency vote.
It has been suggested that putting the regional and constituency votes on a single ballot paper caused confusion.
There was also a separate ballot paper for the local authority elections, which used a different voting system.