Hello, I've been over the HMRC guidance and related sites lots of times but still unsure. Apparently nowadays you can show 'exceptional and relevant' reasons for late Appeals (Mandatory Reconsiderations) - examples given are being in hospital or out of the country. The longer it goes on, the better the reason needs to be. What about when the person was around but they have chronic language/cultural barriers that led to a delay, combined with the fact that the HMRC Compliance Office phone was and is apparently set to permanently engaged (not sure if the notorious Concentrix). The person did send a letter a little past the 30 days deadline but the Compliance Office decided it didn't have quite the exact required wording to trigger a Mandatory Reconsideration, so they simply ignored it. There's then been several further months of inaction until now. Alternatively, 'Official Error' review can be requested for a long time afterwards. But can anyone explain what counts in laymans terms? In this case it would be the Compliance Office phone number never answering (acknowledged as a 'recurring issue' by an HMRC official); the stated reason for the original query appears invalid (their own website specifically says child benefit cannot be considered in deciding main responsibility - at least if there's a dispute which there wasn't here); a decision to remove a child without specific evidence (only lack of reply to a confirmation question - this strategy has been criticised in tribunals before); not contacting the other responsible parent (logically one had to be responsible if the other wasn't according to them). Thanks in advance for anything.