HMRC has updated its Foreign Account Tax Compliance Act (FATCA) registration guidance to inform of the time lag between registration and reporting
FATCA requires financial institutions (FIs) outside the US to pass information about their US customers to the US Internal Revenue Service (IRS).
Those submitting a FATCA return (either an agent, or the UK FI itself) must first register with HMRC using HMRC's online services at http://www.gateway.gov.uk/
According to HMRC’s updated guidance, once FATCA registration is complete, a registrant will need to wait approximately 24 hours before they can file their report.
The updated guidance is available at https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/406699/FATCA_registration_guidance_v0_2.pdf