Penalties for Failure to Notify: in what circumstances is a penalty payable: reasonable excuse: what is a reasonable excuse
A person will not be liable to a penalty if they have a reasonable excuse for failing to notify on time and they remedy that failure without unreasonable delay after the excuse ends.
There is no statutory definition of reasonable excuse, which “is a matter to be considered in the light of all circumstances of the particular case” (Rowland v HMRC  STC (SCD) 536 at paragraph 18). For example, in Anthony Wood trading as Propave v HMRC (2011 UK FTT 136 TC 001010), the First Tier Tribunal applied this definition in their decision released on 23 February 2011.
HMRC consider reasonable excuse to be something that stops a person from meeting a tax obligation despite them having taken reasonable care to meet that obligation. It is necessary to consider what a reasonable person, who wanted to meet their obligation would have done in the same circumstances and decide if the action of the person met that standard as outlined by Judge Medd in The Clean Car Company (LON/90/138X)
‘One must ask oneself: was what the taxpayer did a reasonable thing for a responsible trader conscious of and intending to comply with his obligations regarding tax, but having the experience and other relevant attributes of the taxpayer and placed in the situation that the taxpayer found himself at the relevant time, a reasonable thing to do? Put in another way which does I think alter the sense of the question; was what the taxpayer did not an unreasonable thing for a trader of the sort I have envisaged, in the position that the taxpayer found himself, to do?’
Whether a person has a reasonable excuse will depend on the particular circumstances in which the failure to notify and the abilities of the person who has failed. What is a reasonable excuse for one person may not be a reasonable excuse for another person.
An unexpected combination of events may together be a reasonable excuse.
If there is a reasonable excuse it must exist throughout the period of the default.
It is not possible to give a comprehensive list of what might be a reasonable excuse as each case will depend on the specific circumstances. CH71560 gives some examples of what could be a reasonable excuse.
The law does however specify two situations that are not reasonable excuses. These are