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FeaturesMaking Tax DigitalUpdated February 20, 2026

v1.0.8: National Insurance Number Collection & Validation

v1.0.8: National Insurance Number Collection & Validation

Release spotlight — A closer look at what's new in v1.0.8 and why it matters for UK landlords using Making Tax Digital.

Background

HMRC's Making Tax Digital (MTD) API requires each landlord to supply their National Insurance Number as part of the sign-on and submission process. Without a valid NI Number on file, quarterly tax submissions cannot be authorised and will be rejected at the HMRC gateway.

Prior to this release, the NI Number was not collected or stored by the platform. v1.0.8 closes that gap.

What Changed

1. NI Number Capture in the HMRC MTD Sign-On Flow

Landlords are now prompted to enter their National Insurance Number during the HMRC MTD sign-on process. The field appears at the appropriate step in the authentication journey, keeping the experience in context with the other identity information HMRC requires.

2. UK Format Validation

Before the value is accepted, it is validated against the standard UK National Insurance Number format:

AB 12 34 56 C

Specifically:

  • Two letters — first prefix (certain letter combinations are disallowed per HMRC rules)
  • Six digits — in three pairs
  • One letter — suffix, A, B, C, or D

If the entered value does not match this format, the user sees a clear validation error and cannot proceed until a correctly formatted NI Number is provided. This prevents malformed data from ever reaching the HMRC API.

3. Secure Storage Against the Landlord Profile

Once validated, the NI Number is stored securely and linked to the landlord's user profile. It is:

  • Persisted — no need to re-enter it for future quarterly submissions
  • Associated with the correct user — scoped to the individual landlord's account, not shared across profiles

Impact on Quarterly Submissions

The NI Number is a required field in HMRC's MTD submission payload. With this release:

  1. New users completing the HMRC MTD sign-on will be guided to provide their NI Number before their first submission.
  2. The submission pre-flight check will confirm a valid NI Number is on file before contacting the HMRC API, avoiding unnecessary failed requests.

What You Need to Do

If you are an existing user who has not yet provided your NI Number, you will be prompted to enter it the next time you initiate an HMRC MTD sign-on or attempt a quarterly submission. Have your NI Number ready — it appears on your payslip, P60, or any letter from HMRC.

New users will encounter the NI Number field as a standard step during initial setup.

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