It may be little consolation, but 31 October could be seen as something of a concession. Tax returns go out in April and strictly you are supposed to send them back within 30 days of receipt. But once people miss 31 October they risk being charged interest. The risk of incurring interest arises because your tax office may not be able to send you a tax bill, based on your tax return, in time to meet the normal payment date for tax - currently 1 January.
But hang on. What about self-assessment, the new tax system being heavily promoted by a bowler-hatted cartoon taxman in the Inland Revenue's multi- million-pound advertising campaign? Doesn't that have a different calendar?
It does - but self-assessment does not begin in earnest until after next April for most people. The first year to which the rules on self-assessment relate is the current tax year - 6 April 1996 to 5 April 1997. But the main differences - a new-style tax return, the option to work out your own tax bill, and a new timetable - start with the tax returns that will be sent out next April.
Meanwhile, taxpayers may still be grappling with the old-style tax returns, sent out in April in respect of the tax year ending on 5 April 1996.
It's not only the risk of a financial penalty which should give urgency to the task of sending back the completed form, according to the Revenue. Lyn Simpson, a spokeswoman at the Revenue, says: "Because of self-assessment, it's particularly important for you to get your tax affairs up-to-date. If you still have complications at the time of the start of the new regime, it's going to be more difficult to sort everything out and change to the new system."
But there's a good reason why many people who receive a tax return in April allow it to collect dust for six months - the form is daunting. In practice, though, many people will find that only a few sections need completing.
First, read through the whole form carefully and make a note of any sections that apply to you. Then dig out any records you may need - such as a P60 form, or details of savings and investments, and set aside a few hours in a quiet place to finish the job.
Any queries may be answered by the notes sent out with the tax return. But if you have any doubts, contact your tax inspector. Ms Simpson says: "Your first port of call has to be your local tax office. If people want advice on how to fill in the form it's much better to get it before you fill in the form than to make a guess and get something wrong."
"We can explain what people need to do. Local tax offices and tax enquiry centres can certainly help people."
But if you remain unsure what to put or where to put it, or if you find the allotted space on the form too small, use a separate piece of paper. Explain what you are doing and raise any queries in a covering letter. Once completed, take a photocopy of the form in case of any comeback from your tax office.
Fortunately, the majority of taxpayers are spared the annual ritual of completing a tax return. Most of those are employees who owe no more than basic-rate tax, have it deducted under PAYE and have no complications.
But the onus is on the individual taxpayer to declare income or capital gains on which they owe tax, even if they don't receive a tax return. And this year sees a change in the date by which you have to own up.
New rules brought in as a result of self-assessment impose a new deadline for those who do not receive a tax return. Previously, you had 12 months from the end of a tax year (ie from 5 April) in which to declare new sources of income and capital gains. That has been reduced to six months. In other words, 5 October is the date by which you should have told your tax office about new sources of income, about which they did not know, arising in the previous tax year. That deadline has just passed, but there is no need to panic.
If you had new income or made capital gains in the 1995 to 1996 tax year ending on 5 April 1996 but haven't received a tax return, you should get in touch with your tax office now - and make sure you send back a completed tax return by 31 October. But for anyone who has already received a tax return, the 5 October deadline is of no relevance.
In addition, the 5 October deadline only applies where you actually owe tax. Perhaps, for example, you opened a new building society account last year where tax has been deducted from the interest at source. In this case, you won't need to notify your tax office and fill out a tax return unless you are a higher-rate taxpayer.
Similarly, you may have started a new job during the last tax year (or started a second, part-time, or evening job). Again, you don't have to tell your tax office if you're sure that all the income tax you owe has been correctly deducted at source.
Perhaps you started to get a taxable perk, such as company car. In this case your employer should notify the tax authorities through form P11D. And from next year, you must be given a copy of form P11D. But there is no obligation for employers to give out copies of form P11D this year in respect of taxable perks you received up to last April. So if in doubt, tell your tax office about new taxable perks you received. If you have received a copy of form P11D listing perks, make sure it's correct and tell your tax office if there are errors.
Finally those inclined to conveniently forget about tax they might owe should be warned. Penalties equivalent to the amount of tax owed on undeclared income or gains can be levied if you should fail to tell your tax office and the earnings are subsequently uncovered.