The proposed $2.2 billion sale of ASX 200 financial stock Perpetual Ltd (ASX: PPT)'s wealth management and corporate trust units to private equity firm KKR hit another major roadblock on Tuesday.

According to filings today, Grant Samuel, independent expert called in to analyse the deal, didn't recommend going ahead.

This follows an earlier blow last week, where the Australian Taxation Office (ATO) imposed a potential tax bill far larger than Perpetual initially anticipated.

Perpetual shares were last at $20.18 apiece, less than 1% higher on the day.

ASX 200 financial stock's deal hangs in balance

Perpetual informed investors on Tuesday that advisory firm Grant Samuel could no longer recommend the sale.

The firm said the "risk and magnitude" of the increased tax liability weren't attractive to shareholders.

…the Independent Expert has informed Perpetual that the risk and magnitude of the increased potential tax liabilities, if the transaction were to be implemented, mean that it would not be able to form an opinion that the Scheme is in the best interests of shareholders

The ATO's position last week was that the deal would trigger a tax liability between $493 million and $529 million.

This is well above Perpetual's initial estimate of $106 million to $227 million in August, so you can imagine some head-scratching.

But more importantly, the sizeable increase in tax would slice the net proceeds for shareholders.

Perpetual's initial cash return estimate was $8.38 to $9.82 per share. This has now been slashed to $5.74 to $6.42 per share under the ATO's ruling.

The ASX 200 financial stock was "extremely disappointed" and "disagrees with the Commissioner's views".

But Grant Samuel's decision announced today suggests the potential risks of the tax liability haven't been ignored.

What's next?

Perpetual says it and KKR are now in talks to determine the future of the transaction.

While both parties "are engaging constructively", analysts are sceptical that a revised deal will be feasible.

Jarden Securities noted the hurdles the ASX 200 financial stock now faces in getting support for the deal. According to The Australian Financial Review:

In the absence of the tax ruling being overturned, it would appear a material change in terms or consideration would be required to offer shareholders similar total net cash proceeds originally envisaged by KKR's offer.

Meanwhile, Bell Potter retained its buy rating on Perpetual in a note to clients last week, according to The Motley Fool's James Mickelboro.

It says the deal is unlikely to go ahead following the ATO's assessment. However, it likes the ASX 200 financial stock's base business and values the company at $24.76 per share.

Foolish takeout

While not yet officially off the table, Grant Samuel's ruling has potentially put a nail in the coffin for the deal between Perpetual and KKR to go ahead.

There's no saying what will happen next, but the company faces a tough choice: renegotiate terms with KKR or abandon the deal entirely.

Perpetual shares are down nearly 21% both year to date and in the past twelve months.