A parliamentary report has criticised HMRC's poor service in failing to answer more than half the telephone calls it received in the first six months of 2015.
Taxpayers who have missed the 31 October deadline can escape a fine by going online. The deadline for online returns is three months later- on 31 January 2016.
Self-assessment taxpayers face a deadline of 31 October to submit a paper return.
The Chancellor announces an increase in the inheritance tax threshold to £1m for married couples who leave their home to their children or grandchildren.
The 2015-16 tax year starts on 6 April 2015. New allowances and tax thresholds apply: 2015-16 Isas, marriage allowance and the tax-free savings allowance.
Which? reports George Osborne's 2015 Budget delivered at the House of Commons on 18 March
Chancellor will increase the tax-free personal allowance to £11,000 by 2017-18
George Osborne said in his Budget speech that self-assessment tax returns will be replaced by digital tax accounts, akin to 'Pay as you earn'
Which? rounds up what we already know about Chancellor George Osborne's Budget speech, set to be delivered on March 18 2015.
Practical advice for anyone who has yet to make their self-assessment tax return online.