BX9 1AS is an artificial post code and it is not on the Royal Mail database. Letters received at BX19 1AS are opened, scanned and distributed to other HRMC offices.
Gov.uk website says that for couriers a physical address should be used. Check https://www.gov.uk/government/organisations/hm-revenue-customs/contact/couriers
Hope it helps
Thanks for your reply.
Just one clarification... You mentioned that the completed form should be validated by the Spanish tax authorities, etc. I was told that the local authorities do not - and they can not, validate DT forms. Instead, one needs to obtain a "Residencia Fiscal en Espana Convenio" (Spanish certificate of Residence) and attach it to the completed DT form.
I have completed the DT form for the new pension, attached the Spanish Resident Certificate and posted the docs to HMRC.
I am a Spanish Resident and under the Double Taxation Agreement, I’ve been paying tax only in Spain for two UK pensions, tax code “NT”.
In August 2023, I started drawing a third pension and the first payslip had a tax code “1257L M1”. The second payslip (6-September-2023) shows a tax code “25T M1” and includes a message “As instructed by HRMC”. (NB my PTA shows the tax code as 25TX)
I am not sure what to do about this inconsistency, could you please advise?