Here's an explanation of what it was we did that isn't against EFL rules......
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The accounts that clubs have to produce every year are both historic records of all the money that has gone in and out of the business but also a snapshot of its value.

A club’s income from broadcasters, sponsors and ticket sales is relatively easy to measure and goes in the profit columns, while maintenance costs, rent and salaries go in the debit columns. Take the latter away from the former and you have that year’s profit or — if it is the Championship we are talking about — loss.

But how clubs account for transfer fees and the value of their most important assets, the players, is a bit trickier as it hinges on amortisation: the principle of gradually writing off what it cost you to buy that asset over time.

Every asset a club owns – computers, lawnmowers, office equipment, the training ground, stadium and so on – loses a chunk of its value over time.

Footballers are no different: their value reduces over the length of their contracts until they reach zero, the end of the deal, when they can leave on a free transfer and have no further value to the club. Their value has therefore been amortised or, in the Middle English sense of the word, killed.

This also has an impact on the profit/loss equation, as the fees paid for the players are also evenly spread over the lengths of the contracts. So a £3 million fee for a player on a three-year deal is listed as a £1 million cost in the next three sets of accounts.

Every football club does this. Apart from Derby. They used to do it like everyone else but in 2015 they announced a subtle but significant change to their accounting practices.

“The costs associated with acquiring players’ registrations…are capitalised and amortised over the period of the respective players’ contracts after consideration of their residual values,” the club said.

“After consideration of their residual values” is the key bit there, as football finance expert Kieran Maguire has explained in his recently published book The Price of Football.

“Consider the following,” he explained. “Fulchester Rovers sign a player for £12 million on a four-year contract. Most clubs would therefore have an annual impairment charge of £3 million.

“If the club, however, allocates a residual value of the player (residual value is the expected value of the player at the end of the contract) of say £8 million, then the annual amortisation charge falls to £1 million (£12 million-£8 million/4).

“This would boost profit or reduce losses by £2 million in a year.”

Can you see how this might present a problem for a regulator trying to apply spending controls or a company being regulated in this way that might have overspent?

Derby, as their statement makes defiantly clear, believe they have done nothing wrong as they told the EFL they were making this accountancy change, the EFL did not object and they have not hidden the fact they were doing this.

And there is no question of Mel Morris’ club hiding losses or double-counting profits, as this method of valuing their players reduces the amount of money they can claim on the credit side when they sell a player. In other words, their annual amortisation costs are the lowest in the league but so are their player-trading profits.

The problem, however, is that this method gives the club, not the market, the power to assess a player’s value, and can therefore, in theory, be manipulated to deal with potential financial fair play issues.

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So, no EFL rule broken yet we are still guilty and are now waiting to find out what, if anything, the punishment might be.

Text above taken from another forum. I've not provided a source as there wasn't one given and I don't know where it's from. I have tried to find the source using Google but it hasn't come up with a link matching my search criteria.