Japan Budgeted 3%. The 30-Year Bond Said 4%.

Japan's 30-year government bond reached 4.20 percent this month, a record since the tenor was first issued in 1999.

Tokyo's FY2026 budget assumed 3 percent on government bonds. The Finance Ministry raised that assumption from 2 percent in fiscal 2025, already conceding ground to the market. The 30-year cleared that floor by more than a percentage point before easing to 4.00 percent on May 22.

The gap has an origin. From 2016 to 2024, yield curve control kept the 10-year near zero, and the BOJ would buy whatever volume the market could not. At its peak, the BOJ held 46.3 percent of all outstanding government bonds.

The BOJ has been retreating since March 2024. Quantitative tightening cut $502 billion from its balance sheet by January 2026, with JGB holdings falling to ¥544 trillion. Monthly purchases were trimmed by roughly ¥400 billion per quarter, while the policy rate reached 0.75 percent by December 2025, the highest since 1995.

Private demand has not replaced the BOJ at the same price. Two of the preceding three 30-year auctions drew below the 12-month average, in January and again in April ahead of the Iran deadline. The May 14 auction cleared above the 12-month average, but only at approaching-record yields, with the 30-year then pushing to its all-time high before the month ended.

The Supply Pipeline

Meanwhile the issuance pipeline is widening. Japan's FY2026 budget totals ¥122.3 trillion, the second consecutive all-time high. Debt-servicing costs hit ¥31.3 trillion, one yen in four of all government spending, also a record.

New bond issuance is projected at ¥29.6 trillion against outstanding central and local debt of ¥1,344 trillion, roughly double Japan's GDP. Prime Minister Takaichi has also called for a supplementary budget to address raw-material costs from the war, adding to the supply pipeline before markets have cleared the current one at comfortable spreads.

The arithmetic implies a mismatch the FY2026 budget cannot absorb at current yield levels. Outstanding debt of ¥1,344 trillion adds roughly ¥13 trillion in annual interest cost per additional 100 basis points. The FY2026 budget was priced for a market the BOJ was still holding together.

The Finance Ministry sets its FY2027 bond-rate assumption in the August budget round. Takaichi's proposed supplementary budget adds to the supply pipeline before that round. On May 22, after a record run to 4.20 percent, the 30-year sat 100 basis points above Tokyo's current planning number.