It is easy to say that a company should be separated, but difficult to make it happen. That’s especially true in the case of the spin-off plans for Ernst & Young, whose partners will vote in the coming months to separate the company’s consulting business from its auditing division. Strategically, it has its charms. From a logistical and mathematical point of view, this is a nightmare for numbers experts…

It is easy to say that a company should be separated, but difficult to make it happen. That’s especially true in the case of the spin-off plans for Ernst & Young, whose partners will vote in the coming months to separate the company’s consulting business from its auditing division. Strategically, it has its charms. From a logistical and mathematical point of view, this is a nightmare for numbers experts.

EY split because regulators in the UK and other countries wanted it, but also because it made sense. Accounting firms are often unable to audit companies that are also consulting clients, so being two separate companies, most likely with the consultants as a public company, would allow EY to squeeze all the profits out of it. Chief Executive Carmine Di Sibio estimates it could generate $10 billion in revenue, on top of the $45 billion annually the group earns now.

But in practice it is not easy. Unlike a public company, where shareholders can only vote once to approve the dissolution, EY must organize local voting in some 75 countries. In some, a simple majority is sufficient, in others a two-thirds support is required. In some places one vote is given to each pair; in others, power is distributed according to the capital each person has. And elsewhere, partners with certain accounting qualifications get a separate vote.

Determining the valuation is no less problematic. If the company splits, the audit partners will exchange their share of the consulting business for the consulting audit business. The audit partner will receive a certain amount of cash for solving problems. But the assessment will be based on assumptions. Pricing consultants isn’t all that difficult: competitor Accenture is trading at less than three times its estimated revenue for the year, according to Refinitiv. But no major US consultancies are publicly traded.

EY sold its original consultancy in 2000 to the Capgemini computer company in exchange for stock. Partners watched in despair as the buyer’s stock fell 95% in two years, and then EY rebuilt their consultancy after the non-compete agreement expired. This time there is no need to worry about the actions of buyers, but valuation still matters. The owners of a company are also its employees, so an agreement in which one party benefits significantly better than the other can cause dissatisfaction among workers. Auditors and consultants are trained to be critical of agreements and judgments; getting them to stick to this plan will test EY.

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