If you manage your HMRC reserve in quarterly chunks rather than monthly, this view puts the quarterly figure front and centre alongside the underlying annual estimate.
Updated for 2026/27. Uses UK tax bands and HMRC/GOV.UK guidance. Estimates only — not tax advice.
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Self Assessment checklist, expense tracker, payments on account calendar and more — all in one practical PDF. Updated for 2026/27.
Managing Self Assessment reserves in monthly chunks works well if you are paid monthly. For those with irregular income, project-based earnings or quarterly invoicing cycles, reviewing the reserve quarterly can be more natural.
This calculator puts the quarterly reserve figure front and centre: the annual combined income tax and NI bill divided by four. Use it to set a quarterly review trigger — checking the reserve against what has actually been set aside.
Last updated July 2026. Written and reviewed by James Whitfield against current GOV.UK and HMRC guidance. Estimates for planning only — not tax, accounting or financial advice.
Figures reviewed for the 2026/27 tax year (last updated July 2026). Source: GOV.UK.
From 6 April 2026, Making Tax Digital for Income Tax is mandatory for sole traders and landlords with qualifying income over £50,000. That means keeping digital records and sending HMRC a short update every quarter through recognised software, instead of one Self Assessment at year end. The threshold drops to £30,000 in April 2027 and £20,000 in April 2028, and HMRC reckons around 860,000 people are in the first wave.
HMRC-recognised software includes FreeAgent, Xero, QuickBooks, Sage and Zoho Books. FreeAgent is free for Mettle and NatWest business banking customers. There are no penalties for late quarterly updates during 2026/27.
Keeping a separate account for business income and expenses makes Self Assessment and record-keeping considerably easier.