MTD ITSA Quarterly Deadline Calculator (UK Landlords, 2026)

Making Tax Digital for Income Tax Self Assessment (MTD ITSA) is the biggest change to landlord tax administration since self-assessment itself. From 6 April 2026 it becomes mandatory for unincorporated landlords (and sole traders) with combined gross qualifying income above £50,000 in the 2024/25 tax year. From 6 April 2027 the threshold drops to £30,000, and from April 2028 (proposed) to £20,000. Below the threshold you stay on the existing annual self-assessment return until further notice.

The mechanical change is significant: instead of one return after the year-end, you submit four quarterly updates plus a Final Declaration. Each quarterly update reports cumulative income and expenses to HMRC by the 7th of the second month after the quarter ends. The standard quarter dates are 5 July, 5 October, 5 January and 5 April, with submissions due 7 August, 7 November, 7 February and 7 May respectively. Calendar-quarter reporting is also allowed for businesses that find it operationally easier (1 April / 1 July / 1 October / 1 January) but you must elect for it on each return, not retrospectively.

The Final Declaration replaces the current SA100 + SA105 combo and is due 31 January after the tax year ends — same date as today, but the inputs come from the four quarterly updates and any End-of-Period Statement adjustments. Any tax owed is still payable by 31 January, and Payments on Account remain in place under the same 50/50 rule.

Joint ownership is a common stumbling block for landlords. Each owner has their own MTD ITSA threshold and their own quarterly filing obligation. Two spouses jointly owning one property each receive 50% of gross rent for threshold purposes; if combined rent is £80,000, each is at £40,000 — so neither hits the £50k 2026 threshold, but both will hit £30k from April 2027. Plan ahead: software, accountant capacity and quarterly bookkeeping cadence all need to be in place before the year starts, not mid-quarter.

Penalties for late MTD submissions move to a points-based system. Each missed quarterly update earns one point; at four points (one full year of misses for quarterly filers) a £200 penalty crystallises. After the penalty you stay at the threshold until you submit on time for two consecutive periods, when points reset. Late payment of tax follows the existing regime: 5% surcharge at 30 days, another 5% at 6 months, another 5% at 12 months, plus daily interest from the original due date.

This calculator takes your tax-year start, optional quarter election and last-year qualifying income, and tells you (i) whether you are mandated for the year, (ii) the exact deadlines for all four quarterly updates plus the Final Declaration, and (iii) the point at which Payments on Account are due. Use it to set calendar reminders 14 and 1 days before each filing deadline — inside LetCompliance the same logic powers the dashboard’s tax-deadline ladder, with WhatsApp / email reminders.