Financial reporting has sign conventions, XBRL has a rule

In my previous post, I looked at how a lack of clear best practice around the naming of concepts and elements has contributed to the confusion around sign conventions in XBRL.  I believe that another contributing factor is that the sign conventions used in financial statements are not trivial, and actually quite subtle.

Let’s take another look at the example from my first post:

Turnover 518 498
Cost of sales (321) (299)
Gross profit 197 199
Administrative expenses (211) (105)
Operating profit/(loss) (14) 94

You might also encounter a different presentation of exactly the same data:

Turnover 518 498
Cost of sales 321 299
Gross profit 197 199
Administrative expenses 211 105
Operating profit/(loss) (14) 94

Different jurisdictions seem to converge on one approach or the other, but the point is that either approach is valid.  The same is not true in XBRL.  When it comes to signs in XBRL, there’s a right way to do it, and a wrong way to do it.

In the above examples, we changed the sign of certain numbers on the statement, but we did not change the meaning.  If you change the sign of a number reported in XBRL you will always change the meaning.

When humans read financial statements, they use domain knowledge and context to correctly understand the figures.  I know that companies do not usually report a negative cost of sales (domain knowledge), and a quick check of the figures above and below (context) confirms that in neither case are the suppliers paying the company!

XBRL facts are designed to be understood independently, without the need for context or domain knowledge.

To illustrate the issue, imagine the accounts above had an additional line item:

Taxation 100 (50)

In one year the company paid tax, and in the other it received a tax credit, but which was which?  In the context of the first table, I’d expect this to represent a tax credit of 100 and a tax charge of 50, but in the context of the second table, I’d assume the opposite meaning.  Without the context, it’s completely ambiguous.

By contrast, the sign to be used in XBRL is completely prescribed.  Ask the question, “What was the taxation?” If you answer “100”, then tag a positive number.  If you answer “actually, there was a tax credit of 100” then tag a negative number.

In the last two posts we’ve seen that tagging a value with the correct sign in XBRL is easy, provided that:

  1. You can correctly understand the figure that you are looking at, and you may have to use context and domain knowledge to do this (even if you don’t realise that that is what you are doing); and
  2. The meaning of the concept (which includes its sign convention) is accurately captured in its name.

If you’ve been following XBRL for a while, you might be surprised that I’ve got this far with no mention of balance attributes.  We can’t avoid them forever, so in my next post I’ll be looking at whether they have anything to add, or if they merely contribute to the confusion.

Getting the sign right: Names, labels, and extensions

In my previous article, I demonstrated a simple technique for getting the correct sign when tagging a number in XBRL.  You may have noticed that I was somewhat casual with the notion of concepts having a “name”.  If you’re familiar with the details of XBRL, you’ll know that concepts have an “element name” and typically have at least one label.  Which of these was I referring to?

It is common practice in XBRL to use the standard label to give a concept a human readable name.  The purpose of a name is to unambiguously identify the meaning of a concept, and part of that meaning is the sign convention.  Making a profit and making a loss are two very different things, and if the name of the concept doesn’t make it clear which of these things the concept represents, then it’s not a very good name.

Examples of good names would include:

  • Profit
  • Profit/(Loss)
  • Increase in Accounts Receivable
  • Increase/(Decrease) in Accounts Receivable

Examples of bad names would include:

  • Profit or Loss
  • Change in Accounts Receivable

(the last one is border line – you might reasonably assume that a positive “change” is an increase, but it’s not explicit, and it’s not the sign convention that you’d expect to see used when displaying the concept on a Cash Flow statement)

A more unconventional name like “(Increase)/Decrease in Accounts Receivable” would also be acceptable but note that this is a different concept to one called “Increase/(Decrease) in Accounts Receivable”.

If the idea that a concept should have a name, and that that name should make it clear what the concept means is sounding a bit obvious, then good – it is obvious!

The problem with element names

A concept also needs to have an element name.  This serves a different purpose, which is to provide a unique identifier for the concept in an XML document.  Human readability is not the primary concern, although most implementations have chosen to use meaningful names (e.g. ProfitBeforeTax), rather than arbitrarily generated identifiers (e.g. “c1234”).

XML imposes some constraints on what constitutes a legal element name, most importantly disallowing spaces and most punctuation.  This means that we can’t simply use the standard label as an element name.  Most implementations have adopted an approach of taking the standard label, stripping out punctuation and removing some connective words such as “and”.  This approach is encouraged by FRTA, although an exact rule is not spelt out.

The approach has the unfortunate side effect of turning clear concept names (i.e. standard labels) into rather more ambiguous element names.  For example:

Concept Name         Element Name
Profit/(Loss) ProfitLoss
Increase/(Decrease) in Accounts Receivable IncreaseDecreaseInAccountsReceivable

Such names undermine the notion that XBRL concepts have a clear and unalterable meaning, and that that meaning includes the sign convention.  I suspect that elements such as the above have caused at least some of the confusion about how signs work in XBRL.

There is a very simple approach that would remove this confusion, but it’s not one that has made it into any published best practice that I am aware of, and that is to drop portions of the label that indicate the negated meaning when forming an element name.  For example:

Concept Name         Element Name
Profit/(Loss) Profit
Increase/(Decrease) in Accounts Receivable IncreaseInAccountsReceivable

If you’re uneasy about this approach, remember that the element is just a unique identifier.  It is not intended to be a descriptive label, so the fact that it does not spell out the meaning of a negative value is unimportant.

Extensions and the SEC

In my view, the confusion around signs in XBRL has been fuelled by a number of details of the implementation of XBRL at the SEC.  In the SEC implementation, preparers submit not only an instance document, but also an extension taxonomy allowing preparers to customise the taxonomy to better match their financial statements.

The SEC rule (33-9002) that enabled the use of XBRL for SEC Filings, requires filers to change the labels of standard concepts in the US GAAP taxonomy to match those on the company’s financial statements.  You can argue about whether that’s a good idea or not, but doing so opens the door to confusion around sign conventions.

The text of the rule gives the example of a company relabeling “Gross Profit” as “Gross Margin” as they are “definitionally the same”.  Seems harmless enough, but what about if the line item in your financial statements is “(Increase)/Decrease in Accounts Receivable”?  Should you change the standard label of the US-GAAP concept from “Increase/(Decrease) in Accounts Receivable” to “(Increase)/Decrease in Accounts Receivable”?  In my view doing so is absolutely unacceptable: an increase in accounts receivable is not the same as a decrease in accounts receivable, so changing the name of a concept in this way is very misleading.

The SEC system does provide an appropriate way to handle this situation (negating labels) but the guidance in the Edgar Filing Manual could be clearer.  Rule 6.11.1 instructs filers to “Assign a label of an element used in an instance the same text as the corresponding line item in the original HTML/ASCII document” but nowhere in this rule does it suggest that assigning a standard label that implies the opposite sign convention is unacceptable.  6.11.6 explains how to use negating labels, but does not explain what you should do with the standard label.

Proposed new best practice

I believe that much of the confusion around XBRL sign conventions could be removed by clearly documenting two pieces of best practice:

  1. The element name must reflect the meaning of a positive value reported against the concept.  If the element name is being formed from the standard label, parenthetical indications of negative meanings should be removed.  In other words, a concept called “Profit/(Loss)” should result in an element name of “Profit” not “ProfitLoss”.
  2. When using an extension taxonomy to re-label concepts, it is never acceptable for a standard label to change the meaning of a concept, and meaning includes sign.  For example, “Increase/(Decrease) in Accounts Receivable” must not be re-labelled as “(Increase)/Decrease in Accounts Receivable”.  The correct place for such a label is as a negated label.


Sign conventions in XBRL: it’s just not that difficult!

One of things has continued to surprise me with the adoption of XBRL is the amount of discussion that the question of tagging figures with the correct sign can generate.   Brendan Mullan recently managed to start no fewer than 12 separate threads on this topic on the xbrl-public list, some of which resulted in significant further discussion.

Marking up figures in electronic format is not a new phenomenon, and I’m not aware of any other domains that have managed to get so tangled up in sign issues.  What is it about the application of XBRL to financial reports that causes such difficulty?  I have some ideas, but first let’s look at how to do it right.

All you need to know to get the sign right

Let’s consider the following extract from a Profit and Loss statement:

Turnover 518 498
Cost of sales (321) (299)
Gross profit 197 199
Administrative expenses (211) (105)
Operating profit/(loss) (14) 94

There’s a really simple way to get the sign right in XBRL, every time.  Simply take the name of the concept that you’re using to tag the figure, and turn it into a question by prefixing it with “What was the… ”

For example, suppose our concept is called “Cost of Sales”.

Question: What was the Cost Of Sales?

Answer: £321,000

Even though the figure in the accounts is shown as “(321)”, you wouldn’t answer that question by saying “minus £321,000”, would you?  So we tag a positive number.

On the other hand, if in your answer you need to correct the question, then the sign should be negative:

Question: “What was the Operating Profit?

Answer: “Actually, there was a loss of £14,000.

Our answer is the opposite of the question that was asked, so we’d tag a negative number against a concept called “Operating Profit”.

Sometimes the concept name will be more explicit about the sign convention.  For example, you might have a concept called “Increase (Decrease) in Accounts Receivable”.  In this case, just ignore the bit in brackets, so your question becomes:

Question: “What was the Increase in Accounts Receivable?

If your answer starts, “actually there was a decrease…” then you should tag a negative number.  Otherwise, you should tag a positive number.

It really is that simple.  Nothing to do with balance attributes, negated labels, calculation weights or any of that stuff.

How did we end up in such a muddle?

There’s a number of reasons why what should have been a really straightforward issue has become confused into something much more complicated.  I’ll address these in a series of follow-up articles: