MMTAR Tranche Two Day One: SA/CT Firms Without ASA Must Register
As of 19 August 2026, day one after tranche one closed, HMRC’s Modernising and Mandating Tax Adviser Registration tranche-two window is open through 18 November for advisers with SA or CT agent accounts but no ASA.
Yesterday — 18 August 2026 — HMRC closed the first Modernising and Mandating Tax Adviser Registration (MMTAR) window and opened tranche two. As of 19 August, advisers who hold a Self Assessment or Corporation Tax agent account but still lack an Agent Services Account (ASA) are inside a three-month application window that runs through 18 November 2026.
HMRC’s GOV.UK guidance and MTAR10800 manual confirm you can continue interacting with HMRC for clients during the three-month window and while HMRC considers a timely application. Incomplete evidence packs still create later access risk — treat day one as an evidence-mapping day, not a soft start.
Confirm you are in tranche two
You are typically in tranche two if, immediately before 18 August 2026, you did not have an ASA but did have a specified Self Assessment or Corporation Tax agent account, and you are not in the later payroll-only or financial-services cohorts. Use HMRC’s interactive checker rather than assuming a sibling office’s ASA covers every agent ID.
Advisers who already hold an ASA do not re-register in this phase; HMRC will contact them through the ASA if further information is needed. Payroll-only firms sit in a later window (18 November 2026 to 18 February 2027) and should not confuse that timetable with today’s open window.
Day-one ASA application priorities
Map every agent ID across offices and name an owner for each ASA application so nobody is left off the register.
Assemble identity evidence, AML supervision status, supervisory body details, and ownership information before partners invent lists under client pressure.
Open the ASA application early in the three-month window so HMRC processing time does not collide with autumn MFA automatic activation (28 September to 15 October).
Keep today’s MFA voluntary activation and tomorrow’s third-party data consultation close as separate named workstreams.
How FinnAccountings helps while registration beds in
Clean client ledgers reduce pressure when partners spend August on ASA applications. FinnAccountings helps Ireland and UK advisers and business owners prepare bookkeeping and tax packs with Chartered Accountant insight before you or your ICAEW/ACCA or Chartered Accountant (Ireland) adviser files. Start a free trial for review-ready drafts — we prepare records; we do not register you with HMRC or file agent applications on your behalf.
Related reading
Use yesterday’s day-of close briefing for the tranche-one / tranche-two handover narrative.
Keep the weekend tranche-two checklist beside the application form.
Keep the agents’ critical fortnight overview handy for the 18–20 August cluster.
HMRC’s 4,000+ application volume update sits beside the open November window.
Sources & references
This article draws on official guidance from the sources below.
- Check if and when you need to register as a tax adviser with HMRC
HM Revenue & Customs · Accessed 2026-08-19 - MTAR10800 - when tax advisers must register and transitional arrangements
HM Revenue & Customs · Accessed 2026-08-19 - Tax advisers: one month left to register under new rules
HM Revenue & Customs · Accessed 2026-08-19
Put this advice into action
FinnAccountings automates bookkeeping, tax, and VAT for Ireland and the UK.
Try AI accounting free