Penalties and interest: non HMRC guidance or advice is incorrect
The text in CCM10610 and CCM10630 only relates to HMRC guidance or advice. Where the customer says they followed advice given by someone else you will have to judge each case on its own merit. If they say they followed advice from a friend or neighbour or relative unless that person normally acts as an adviser for tax credit matters you should not usually accept that following such advice escapes a penalty. The customer has not taken reasonable steps to ensure they have met their obligations correctly.
If they say they have followed advice given by an adviser such as the Citizens Advice Bureau or a Job Centre Plus or similar you might conclude they have taken all reasonable steps to make a correct claim. You would need to bear in mind the error they had made, whether it is likely they would have received such advice and whether the customer has previously made any incorrect claims or failed to notify changes of circumstance. If you conclude they have not acted negligently then there is no penalty for an incorrect claim. If you conclude, that as a result of following guidance from a legitimate source, they genuinely did not think they had to tell us about a change of circumstances then there will be a reasonable excuse for not doing so and no penalty will be charged.