Inside MMTAR: The Background
MMTAR is HMRC's new registration system for anyone paid to deal with HMRC on someone else's behalf. The aim is to raise standards across the tax advice industry and give clients more confidence in who they're trusting with their finances. Until now, anyone could set themselves up as a paid tax advisor with relatively little oversight from HMRC directly, and MMTAR is meant to close that gap by bringing every paid advisor onto a single registered, traceable system. If a client of yours needs the mechanics, our guide on how to authorise an accountant with HMRC walks through the ASA side of the relationship.
Phase One ran from 18 May 2026 to 18 August 2026 and targeted new advisors, or those without an ASA, self-assessment account, or corporation tax account. This was, by design, the smallest and least established slice of the advisor market. HMRC reports that more than 4,000 applications were submitted, with over 2,000 accounts created in that window, which HMRC has pointed to as an early sign that the registration process itself is working smoothly.
Phase Two, now underway, moves on to advisors who do have a self-assessment or corporation tax account but haven't yet set up an ASA. This is a larger and more established group than Phase One, made up of advisors who've been operating for a while but never needed an ASA for their day-to-day work. They have until 18 November 2026 to register. If you're weighing up whether to pay for that support at all, our piece on claiming accountant fees as an expense is a useful companion read
