Chas Roy-Chowdhury, the Head of Taxation at ACCA, told the BBC that those who are yet to submit their return online will need to allow sufficient time to ensure it is completed by the deadline.
Furthermore, he said that anyone who is new to submitting their details online will need to apply for an activation code, with a deadline of January 21st in place for this.
Mr Roy-Chowdhury added: "While self-assessment is all about getting our tax returns completed accurately and filed on time, it is also about paying the tax.
"Added to this, we do all this work free for the government, but if we make a mistake, or are late filing the return or paying the tax, then we may have to pay a penalty."
Anyone who misses the deadline will face an immediate £100 penalty, irrespective of whether there is any tax to pay, with further penalties if it is three, six or 12 months late.
Posted by Emily Smith