Coke - "Diet", "Classic," "Zero" or other - is a brand recognised the world over and accepted as one of the most valuable, with estimates ranging from £40bn to more than £60bn.

The company is justifiably proud, trumpeting the fact in the first line of its annual report. But any investor would be hard-pressed to figure out what Coke thinks the name is worth, since it does not put a number on it - and does not have to.

Accounting has traditionally stuck to what it knows, valuing tangible items such as property, plant and equipment. But with the shift towards a more knowledge-based and service-orientated economy, intangible assets account for more of a business, leaving accountants to grapple with just how much could, and should, go on the balance sheet.

Intangibles vary between companies, ranging from brand value - a figure becoming increasingly precise thanks to sophisticated valuation techniques - through items such as patents and customer lists to more "fuzzy" concepts such as the value of a workforce.

Moves in recent years by accounting-standard setters have leant towards bringing more intangibles on to balance sheets. But this has met with scepticism and resistance from the profession and from analysts aware there is value in the way the numbers are presented.

"There is a feeling the profession is failing to deal with valuation issues and that by not doing so, there is a sense financial reporting is losing its relevance to non-accountants," says Thayne Forbes, joint managing director of Intangible Business, a valuation consultancy.

"You're left with a balance sheet that if it has intangibles, shows them at historic amounts where they're only ever revalued down and not up, so when you look at it, it's impossible to make head or tail of it. You don't even have a breakdown of how the number is arrived at." Coke, for example, splits intangibles into categories such as trademarks and goodwill - and attributes that to operating regions - but it does not give details as to those trademarks, nor how it reached its values.

Intangibles generally appear as the result of a merger or acquisition. Accounting rulemakers have mostly shied away from opening a wider debate about the place of intangibles.

However, they have made a determined assault on acquisition accounting and the use of goodwill, the catch-all title used to cover the difference between the balance sheet value of the acquired business's assets and the price paid.

Both US and international standards require companies to account more fully for intangibles, with the aim of reducing the amount lumped under the infamous catchall. But despite these efforts, intangibles' appearance is haphazard at best. Studies by Intangible Business show that in the first year of IFRS 3, the international standard, more than half of the value of acquisitions by FTSE 100 companies were still accounted for under goodwill, with 17 per cent to tangible assets and 30 per cent to defined intangibles.

Should it be left up to the whims of merger-mad CEOs before intangibles appear or could it become part of regular reporting? Theoretically, there is an argument for more regular use, says Ken Williamson, leader of the financial reporting advisory team at Ernst & Young, who says there is growing comfort among company executives with the more familiar intangibles.

"There is an inherent limitation with the current thinking, since you can have two companies with similar histories in the same marketplace and with similar brands, but one of which has grown organically while the other grew through acquisition.

"The balance sheets would look very different and that doesn't feel right," he admits.

But for Mr Williamson, along with his colleagues, there is much scepticism about the practicalities of doing something about it.

"I'm not sure internally generated intangibles help very much, I think it's likely that analysts would discount them anyway," says Andrew Buchanan, national technical partner at BDO Stoy Hayward.

"An external transaction gives the test of the actual value, so if people started to suggest internally-generated intangibles, I'd feel uncomfortable because of the subjectivity and difficulties around measurement." Steve Taylor, a valuations expert at E&Y, is also wary about the limited usefulness of such subjective valuations.

"It rings warning bells for me," he says. "There is more credibility to an asset if it is on a balance sheet. People look at it and say 'We've got brands, patents that we can sell for cash if we need to,' when that might not really be the case.

"I worry that a less sophisticated user of financial statements ends up being confused by how the assets ended up there and what is truly realisable." This is a debate set to run and run, as valuation techniques become more sophisticated - and more accepted - and businesses continue the shift away from tangible assets, leaving acccountants with some tough choices.

Mr Forbes is confident the trend is turning his way: "Valuation is subjective, yes, and you can argue something is worth a different amount , but there's no excuse for dumping them in goodwill where no one knows what's going on.

"These items are there and they're driving business value."