R&D claim - Addiitonal Information Form

[Hollyeleanor]

Hi

I've posted this on Accountingweb but thought Id try here as well:

I've been filing an R&D claim for a client for a number of years and need to file for 31/7/2023 but include an Additional Information form for the first time. HMRC's guidance indicates that this is done using my Agent Services Account but I cannot see how to add this 'service' to my account and file the form. I've looked elsewhere but all the links seem to relate to a new R&D claim which this is not (and obviously, if it were, we would have missed the 6 month cutoff to notify). Before I give up my morning and try and call HMRC, can anyone help, please?

Thank you