The Murdochs’ 320 million shares stand to get New Fox shares worth about $3.84 billion. All of this would presumably be taxable. (Richard Drew/AP)

Hard as it is to believe, there might be some good news for us average taxpayers buried in the announcement that the Justice Department has agreed to let Disney buy the entertainment assets of Twenty-First Century Fox.

And the good news, if tax expert Robert Willens is right, would be bad news for Rupert Murdoch’s family. Which, it appears, will have to fork over more than $3 billion of federal, state and local income tax if the Disney deal goes through as structured.

And amusingly — at least I find it amusing — the Murdochs’ income tax bill would consume most and possibly all of the multibillion-dollar windfall the Murdochs stand (or perhaps stood) to get from the $19 billion increase in what Disney is paying for the Fox entertainment assets.

Under the initial Disney offer, which consisted entirely of Disney stock, the Murdochs would have had no tax due until (or unless) they sold the Disney shares they got in the deal, or the “spinoff stock” (of which more later) that they and other Fox holders are getting that will own the assets Disney doesn’t want.

I’ll spare you details of what Disney is buying, which my colleague Steven Zeitchik is writing about .

I’ll also spare you as many numbers as possible. And I promise not to mention any specific provisions of the tax code.

How do I know about the tax bite that’s apparently being put onto the Murdoch family by the new, higher Disney offer? From the reports that Willens of Robert Willens LLC has written about the Fox sale since the initial Disney offer in December of about $52 billion of stock for the Fox entertainment assets.

In mid-June, Comcast offered about $65 billion of cash, which Disney topped a few days ago by offering $71 billion, half in cash and half in Disney stock. The fact that there’s a lot of cash in this deal is what triggers taxes for Murdoch (and some other Fox holders, as well).

Now, let me try to show you what’s going on. In a language that approaches English and that you don’t need an MBA in tax to understand.

Here goes:

For reasons I won’t even try to explain, the deal involves Twenty-First Century Fox (which we’ll call 21CF) creating a new company to own the assets Disney isn’t buying, such as Fox News. Stock in this “spinoff” company, which we’ll call New Fox, will go to existing 21CF shareholders.

Under the initial Disney deal, getting shares of New Fox wouldn’t have been a taxable event for 21CF holders, and getting Disney shares in return for the entertainment assets wouldn’t have been a taxable event, either.

But the large amount of cash (about $35 billion) in the new Disney offer changes the tax picture. Now, according to Willens, the New Fox shares that 21CF holders get will be taxable.

In addition, any cash that 21CF holders get from Disney for the properties that Disney is buying will also be taxable.

(The all-cash offer from Comcast — which is probably either cackling about having forced Disney to part with an extra $19 billion or preparing its counter-counter bid or both — would probably have created an even bigger tax bill for the Murdochs et al. That may have had something to do with 21CF’s less-than-thrilled reaction to Comcast’s offer.)

Now, let’s do Murdoch math.

The Murdoch family trust, as we’ve seen, owns about 320 million shares of 21CF. By my read of the stock market’s read of the deal, the New Fox shares that 21CF holders would get are worth about $12 per 21CF share.

(That’s based on 21CF’s recent stock price of about $50 and subtracting the $38 holders stand to get from Disney.)

The Murdochs’ 320 million shares thus stand to get New Fox shares worth about $3.84 billion. All of this would presumably be taxable. “Having a taxable spinoff isn’t something you see every day — or even every year,” quips Willens, the tax maven.

I’m assuming several things here. For one, I assume that the cost of the Murdoch family’s piece of 21CF is roughly zero, for reasons I won’t go into. And that the family trust that owns the stock is subject to federal, New York state and New York City income taxes. I’m also assuming — I hope correctly — that the mutual love affair between Rupert Murdoch and President Trump won’t result in any special rulings from Trump’s IRS or any other part of the government that would benefit Murdoch.

Remember that $3.84 billion.

Now, let’s look at what Disney is paying for the entertainment assets: $38 per 21CF share. Disney says it will pay half of this in cash and half in stock. The Disney stock, as I said, wouldn’t be taxable, but the cash would.

Holders will be able to ask for all cash or all stock or something in between. I’m assuming that the Murdoch family will seek stock for all the $12.2 billion it stands to get. (That’s 320 million shares times $38.)

I’m also assuming that many other 21CF holders will ask for all stock.

Finally, I’m assuming that 21CF holders will collectively ask for lots more stock than Disney is offering. Therefore, these holders will be forced to take some cash.

If the Murdochs end up having to take 40 percent — call it $4.88 billion — of their Disney swag in cash, that would increase their taxable income from the deal to about $8.7 billion. That’s this swag plus their $3.84 billion of New Fox.

Now, for tax calculations. Combine the top 23.8 percent federal income tax rate on long-term capital gains with the top New York state and New York City income tax rates, and you get a total tax rate of about 36.5 percent. Apply that to the Murdochs’ $8.7 billion (by my estimate) of taxable income, and the total income tax runs about $3.2 billion.

Under the old tax law, the Murdochs’ $1.1 billion or so of New York state and New York City income tax would have been deductible from their federally taxable income.

Under the new tax that Rupert Murdoch’s buddy Trump pushed through last year, you can’t deduct more than $10,000 of state and local taxes from your federally taxable income. So by my math, the Murdochs are forking over about $260 million more than they’d have owed last year.

I’m not shedding any tears for the Murdochs. But I found the change in their tax status fascinating. I hope you do, too.