The 2026 BUDGET Gap.
ARITHMETIC OF a CREDIBILITY CRISIS

Fiscal crises rarely begin with one shocking number. They begin when the arithmetic becomes too dependent on multiple optimistic assumptions holding simultaneously: revenue forecasts at the top of their historical range, asset sales scheduled but uncontracted, spending commitments that are politically irreversible and a rates market that remains willing to refinance at spreads that assume the path is sustainable.

This is the structure of the 2026 budget gap across the major G7 sovereigns. It is not a crisis in the sense of market dislocation. It is a slow deterioration in the quality of fiscal projections that eventually produces a repricing event when one of the assumed supports fails.

The desk runs a simple analytical framework: take the official budget projection, stress-test each of the three major revenue assumptions by replacing them with the historical median (not the pessimistic tail, just the median), and calculate the resulting deficit at median assumptions. If the resulting number is more than 1.5 percentage points of GDP wider than the official projection, the desk classifies the fiscal plan as 'optimism-dependent.' The US, UK, France and Italy all meet this classification in 2026.

The CBO's January 2026 baseline projects a federal deficit of 5.1 percent of GDP for fiscal year 2026. That projection incorporates a number of assumptions that the desk's stress-test challenges.

First, it assumes current law revenue, which includes the expiry of the Tax Cuts and Jobs Act provisions in late 2025. If those provisions are extended, which the political baseline strongly suggests will happen, the revenue shortfall relative to CBO baseline is approximately USD 300 to 350 billion per year over the next decade. The CBO cannot incorporate this because it is required by law to score current law, not the politically likely alternative.

Second, the CBO baseline assumes nominal GDP growth of 4.1 percent in 2026. At 3.5 percent nominal growth, which is consistent with the desk's macro view, the deficit widens by approximately USD 80 to 90 billion through the automatic stabiliser and revenue elasticity channels.

Third, the CBO baseline does not include any estimate of the fiscal cost of tariff implementation and its second-order effects on import volume, customs revenue and the broader inflation and growth path.

The UK Office for Budget Responsibility's March 2026 forecast projected public sector net borrowing at 3.4 percent of GDP for fiscal year 2025-2026, leaving approximately GBP 9.9 billion of headroom against the Chancellor's fiscal rules. That headroom was GBP 26 billion in October 2024. The compression reflects growth disappointment, higher-than-expected debt servicing costs and NHS spending overruns.

The desk's view is that the OBR's March 2026 forecast incorporated optimistic assumptions about productivity growth (1.4 percent, versus the desk's view of 0.8 to 1.0 percent) and household consumption growth. At the desk's assumption set, fiscal headroom against the spending rule is either negative or within statistical margin of error.

The gilt market has been patient. 10-year gilt yields remain around 4.50 to 4.70 percent, having recovered from the October 2022 episode. But patience is not unlimited. A second OBR downgrade in October 2026, combined with a fiscal headroom breach, would test the market's willingness to absorb additional gilt supply at current yields.

France's budget deficit is tracking toward 5.2 to 5.5 percent of GDP for 2025, materially above the EU Excessive Deficit Procedure limit of 3.0 percent. The European Commission initiated an EDP against France in 2024 and the formal correction path requires a structural adjustment of approximately 0.5 percent of GDP per year through 2028.

The OAT 10-year spread to Bunds widened from 50bp in early 2024 to a peak of 85bp in late 2024 during the political crisis following the dissolution of the National Assembly. It has since compressed to around 65bp as the current government demonstrated more fiscal discipline than the market feared. But 65bp remains elevated by historical standards and the compression has stalled.

The key variable is whether the 2027 French presidential election produces a government committed to the EDP adjustment path or one that seeks to renegotiate it. A renegotiation attempt would immediately widen the OAT spread and potentially trigger a broader European sovereign risk repricing.

The desk's framework for sovereign fiscal risk positioning: distinguish between sovereigns with credible institutional mechanisms to address fiscal deterioration (US, UK, Germany) and those where the adjustment mechanism is politically impaired (France, Italy, some EM).

For US Treasuries: the fiscal trajectory justifies a term premium above historical average. The desk maintains a preference for shorter duration and inflection-point tactical extensions rather than structural long-duration positions.

For UK gilts: fiscal headroom is thin but the institutional credibility of the BoE and OBR framework is intact. A tactical long at 4.60 to 4.70 percent on the 10-year is reasonable given the BoE easing cycle, but stop-loss at 5.00 percent given the fiscal fragility.