20AUG

OBR fixes 28 October for next forecast

2 min read

17:53UTC

The Office for Budget Responsibility confirmed its next Economic and fiscal outlook for 28 October 2026, the forecast against which Budget decisions will be scored.

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Key takeaway

The OBR will publish its next Economic and fiscal outlook on 28 October 2026.

The Office for Budget Responsibility (OBR), the independent body that produces the official forecasts against which the government's fiscal rules are judged, confirmed that its next Economic and fiscal outlook will be published on 28 October 2026, on a commission from the Chancellor ¹. That document scores Budget decisions: it prices each measure, projects debt and borrowing over five years, and states whether the rules are met.

The OBR made no change during this window to the 1.4% long-run productivity growth assumption that underpins those projections ². Productivity growth determines how fast the economy, and therefore the tax base, expands over the forecast period. A fraction of a percentage point compounded over five years moves the debt path further than most of the tax measures currently being argued about in public.

Some of the pressure on that forecast accumulates without anyone deciding anything. The state pension triple lock, which uprates pensions by the highest of earnings, inflation or 2.5%, is costed by the OBR at £15.5bn a year by 2029-30 , and it grows through a formula rather than through a decision taken in October. A Budget can change tax rates in a morning. It cannot change the assumption about productivity, which the OBR sets on its own evidence, and it changes commitments of that kind only by legislating.

Deep Analysis

In plain English

The Office for Budget Responsibility is the independent body that checks the government's sums, forecasting growth, tax revenue and debt. One of its key assumptions is how fast the economy's productivity, output per hour worked, will grow over the next few years. That assumption is currently 1.4% a year and has not changed in this window. It matters because the OBR uses it to project how much tax revenue the economy will generate, and therefore how much government debt is projected to grow. The OBR's next full forecast, when this assumption could be revised, is due on 28 October 2026.

Deep Analysis

Root Causes

The OBR's medium-term debt projections compound a single assumed productivity growth rate over its multi-year forecast horizon, so a small change to that one number moves the projected debt path by more than most individual tax or spending decisions would.

That is why this desk tracks the 1.4% figure specifically, rather than the OBR's other assumptions, as a leading indicator of whether the October forecast will show a materially different debt path.

What could happen next?

Risk
If the OBR lowers the 1.4% productivity assumption at the 28 October forecast while the defence and pension cost pressures already flagged this year remain in place, the projected debt path would widen from both directions at once.

Source Landscape

This story draws on neutral-leaning sources

Consensus view: The OBR's own publication register shows no change in this window to its 1.4% long-run productivity assumption, the single figure that most affects the scale of its debt projections, with the next full update due at the 28 October Economic and fiscal outlook.

Counter-view: The OBR's own costings elsewhere this year have already flagged two upward cost pressures on the fiscal path that assumption feeds into: a NATO defence spending path the IFS puts at roughly £25bn a year unfunded against plans announced so far , and a state pension triple lock cost now put at £15.5bn a year by 2029-30, roughly triple the original estimate .

Key tension: Whether an unchanged productivity assumption sitting underneath a fiscal picture that has otherwise become more expensive means the October forecast is more likely to show a wider funding gap, or whether the OBR intends to revisit the assumption itself at that publication.

Sources:Office for Budget Responsibility

Mentions:Office for Budget Responsibility →Economic and fiscal outlook →

First Reported In

Update #2 · Three household registers, three answers

Office for Budget Responsibility· 20 Aug 2026

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Different Perspectives

A Treasury official weighing pre-committed claims

The triple lock costed at GBP15.5bn a year by 2029-30 and roughly GBP25bn a year of unfunded defence commitment sit on the sovereign balance sheet regardless of which household register looks best this month. The 28 October forecast, not this week's releases, is where those claims get priced.

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The IFS's warning that assigning 6% to 9% of local income-tax revenue to mayors from April 2028 shifts revenue risk onto authorities that cannot control the tax base concerns every council balance sheet, including those currently comfortable. A council cannot smooth an income-tax downturn the way the Treasury can.

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The PPF's 7800 index reaching 133.0% funded, a GBP271.3bn surplus across 4,838 schemes, is the strongest position this desk has recorded for the index. A member's pension is more secure than it was a month ago, whatever is happening to household insolvency figures elsewhere.

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