The deadline is 30 September if Inland Revenue handle your tax calculations or 31 January if you work it out yourself.
Whether you consider last year's self-assessed tax experience a success or a failure depends on your viewpoint. Inland Revenue spokesman Paul Jeffries says: "Substantially, self-assessment in its first year worked well and we were glad that eight out of nine million taxpayers sent in their returns by the 31 January."
Not all the remaining million will come back as some were issued to people who had stopped earning, and forms issued after October 1997 received an extended deadline.
The Revenue issued 700,000 penalty notices to those who missed the return deadline, but not all of those concerned were liable for the pounds 100 fine. About 140,000 appeals were lodged in response to the penalty notices. The penalty, however, for not submitting a tax return can't be more than the amount of tax due. But a return must be filed for the penalty to be cancelled.
The responsibility of working out tax liabilities now lies firmly with the taxpayer. Many people who last year filed returns in the second half of the period are determined to do it before September 30 to take advantage of the Inland Revenue's offer to do the calculations for them.
Tony Fava, a chartered accountant in Richmond, North Yorkshire, explains: "There's a lot of work involved in getting the calculations right. It's better to let the Inland Revenue work them out and then check their figures against the calculations the accountant has made independently."
If you do your own calculations the chances of making a mistake can be high - and under the self-assessment scheme not only do you have to complete the return by the deadline, but you also have to get it right, or face a penalty.
The most common reasons for tax returns being "bounced" are oversights: failing to sign or date the return, leaving boxes blank and ticking a box to say a supplement applies, but failing to send in the documentation. There are, however, mistakes that affect the substance of the tax return and these are ones that tax preparation software can help avoid.
These include claiming both married couple's and additional personal allowance and entering the net, rather than the gross figure for personal pension contributions if you are an employee. As last year was the first under this new scheme a degree of flexibility was allowed. In most cases where taxpayers filed their returns in time but with minor mistakes, penalties were waived as long as the forms were corrected by 11 February.
Taxpayers were not the only ones who made mistakes in the first year of the new scheme. Software suppliers also had their lapses.
In the earliest version of Intuit's QuickTax 97 users uncovered a string of bugs in the calculation routines of the software. These affected many different aspects including omitting to post age and married couples' allowances and treating a capital loss as if it were a capital gain.
By the time the problems were discovered, some forms produced by the program had already been submitted with errors to the Inland Revenue.
Intuit undertook to pay any charges that arose due to errors in QuickTax 97 and worked with the Revenue to remedy the situation. Intuit spokesman Tony Macklin says no fines were levied: "The Revenue's concern is that people pay the right tax and not to penalise individuals for making errors." Intuit had this year's version of the program, QuickTax 98, completely rewritten by a different team.
Despite these problems, thousands of UK taxpayers found that the tax software enabled them to execute a complex chore easily and with greater confidence. There are likely to be even more users for this year's versions, all of which feature improvements and extensions.
Programs such as QuickTax, TaxCalc and Tax 98 help users complete the tax return by asking a series of questions independently of the Inland Revenue's form. They then transfer information gleaned in this process and fill in the relevant sections of the form. This benefit applies even if you submit your tax return without having worked out your tax liability.
If you miss the 30 September deadline, the computer programs could prove an added advantage.
Which Software, Whose TaxCalc - the UK's best-selling personal taxation software program - is offering TaxCalc 98 to readers of 'The Independent' for pounds 24.99 plus pounds 2.00pp (compared to a RRP of pounds 29.99 plus pounds 3.00pp). Quote reference IN/07. Order by phone on 0990-084 201 or by post to: TaxCalc Order Department, FREEPOST BM4347, Birmingham, B24 8BR. All major credit cards accepted including Diners and Switch; cheques should be made payable to IDP Ltd.