To reinforce the advice in the Guide, please follow up with a phone call even though you have the tracking delivery confirmation. A kindly staff member has 'manually registered' a written one received with two days to go, which was 'on the system' but not 'registered' on the last day. They informed me that senior management have set up for automatic texts to be sent giving a timescale, but this is completely unrealistic due to the overwhelming tide of work, and should be ignored! Presumably the workload is also affecting the registration of postal MR submissions, so please do do the double-check by phone, however annoying the wait. Best to avoid needing to have an argument imho.