It is reckoned that under the system, due to come into operation in the 1996-97 financial year, 9 million people will be required to file tax returns. About half of those are currently unrepresented by tax advisers, says Gerry Hart, president of the Chartered Institute of Taxation, who believes that nearly all of them will seek help of some kind.
The Inland Revenue denies that most people will need advice, pointing out that it has published a guide to the system and that its officials will be available for assistance. But one does not need to be unduly cynical to believe that most people will not go out of their way to contact Inland Revenue nor to suppose that the guide will not be especially easy to understand.
Mr Hart insists, however, that this development is not all good news for his organisation. Just as it has received its royal charter and sees its membership closing on the 10,000 mark, it is faced with the prospect of its image being tarnished by the activities of unqualified tax practitioners.
Since he is managing director of Tax Team, a chain of franchised tax specialists that includes standard return filing among its services, he is not entirely against the arrival of cheap suppliers.
"I don't think our members have anything to fear about people coming in at ridiculously low prices. The concern is if people come in at just a little less than they have quoted," he says.
This is because personal tax work is particularly sensitive to cost. A practitioner has to know what he or she is doing, otherwise they can end up submitting a bill that is substantially more than the estimate or face a loss on that transaction.
Moreover, he warns that some suppliers may get themselves into trouble if they simply make returns on the basis of the information supplied by the taxpayer. "I don't think that's sufficient," says Mr Hart. "You need to anticipate trouble before it arises. How does it compare with the figures put down last year? Are there opportunities to improve the tax position?"
And trouble there is likely to be.Inland Revenue has let it be known that there will be 5,000 to 10,000 random audits a year on top of the investigations into matters where there are grounds for suspicion. Mr Hart has voiced his concern that this could lead to officials going on "fishing expeditions" and has warned practitioners to be on their guard to deal co-operatively, but firmly with them. But overall, he and his organisation are in favour of the developments, which he admits will amount to a "change in culture".
Certainly, Tax Team sees opportunities for expansion in self-assessment. It currently has six offices - with Mr Hart based in Horsham, West Sussex - but expects a significant expansion by March, in time for the introduction of the new rules. Since a report published late last month by the Institute of Chartered Accountants suggests that self-assessment is bound to be extended before long because of the problems of combining it with pay as you earn, further growth cannot be ruled out.
Fittingly, the Institute of Taxation is also on the rise, not only in numbers but, apparently, in influence, too.
A few years back, it appeared to be greatly upset by the chartered accountants having a tax faculty. But recently Mr Hart and Simon McKie, chairman of the faculty and a member of the tax body, appeared together to launch combined ethical guidelines. Mr Hart explains that the new understanding results from the realisation that the tax faculty exists merely to look after chartered accountants who practise tax, while the taxation institute takes in not only them, but also lawyers and those who - like Mr Hart himself - have no other qualification.
At the same time, the institute is establishing good relations with what might be termed the old enemy, Inland Revenue. Mr Hart hopes soon to announce arrangements under which people trained by Inland Revenue can be exempted from certain of the institute's examinations. As he points out, while the leading firms have for years persuaded tax inspectors to turn poacher, there are growing numbers of long-standing Revenue officials being made redundant and looking to continue their careers elsewhere. Having a more portable qualification could help.
Meanwhile, Mr Hart and his colleagues will be poring over the plans for the simplification of the tax system published by the Government this week. It might be expected that this would be the last thing he would welcome, but he insists that the complexity of current tax legislation - a consistent theme of his immediate predecessors - is not of much use to anybody. The Government has realised that enough is enough, he says, while tax professionals are frustrated because they cannot give clients "the degree of certainty they require".
The only problem is that sorting out all this complexity is no simple task. It is reckoned that it will take five years, and a correspondingly large sum of money, and is therefore ripe for being postponed should an incoming government feel that it has more pressing priorities.