The taxman has warned that over 100,000 parents caught out by the government's changes to child benefit have yet to do anything about their liabilities. If they don't act fast, they will face fines of at least £100 - and potentially over £1,000.
So who is at risk, and why?
The problemThe change in question was the government's decision to start taxing child benefit for anyone earning over £50,000. If either parent makes over this amount, they will be taxed the equivalent of 1% of every £100 earned, until a person earning £60,000 will have to pay it all back in tax.
Some 1.1 million people were affected by the change, and they had a choice: they could opt out of receiving the benefit in the first place, or they could complete a self-assessment tax return at the end of each tax year in order to pay the relevant tax on the benefit. Over 390,000 people chose to opt out, leaving the rest to pay through self-assessment
The change was introduced in January 2013, which means some payments fell into the 2012/2013 tax year - for which the self-assessment deadline is just about to hit us - on 31 January.
Not readyThey should all have received a reminder about this back in August, but this week HMRC told The Guardian that more than 100,000 parents have not get registered for self-assessment - that's one in ten of those who were affected by the change.
Even when they do, their first step will be to apply for a code to enable them to file their return online. This has to be sent through the post which Your Money warns can take up to seven days. Given that this is such a busy time for HMRC, parents should apply for the code by 21 January.
FinesAny of the affected parents who miss the deadline will be fined £100 immediately. However, as we reported last week, if they don't rectify this quickly - and pay everything they owe - they will find the fines start building up dramatically.
If you haven't filed by the end of April you'll be charged £10 a day, which will continue to be added to your bill every day for the next 90 days. After that, when you're six months late you'll be fined £300 or 5% of whatever is due (whichever is highest). And six months later you'll be fined another £300 or 5%.
No-one likes filling in their tax return, but clearly it's better than the alternative.