Tier 1 Capital

Tier 1 capital is the portion of a bank’s regulatory capital intended to absorb losses while the bank remains a going concern. Under the Basel Framework, it consists of Common Equity Tier 1 (CET1) plus eligible Additional Tier 1 (AT1) capital, after the regulatory adjustments assigned to those categories.

Key Takeaways

• Tier 1 capital is not a synonym for common equity; it combines CET1 and AT1.
• CET1 is intended to be the predominant and highest-quality part of Tier 1.
• AT1 instruments must satisfy strict permanence, subordination, distribution, redemption, and loss-absorption criteria.
• The Tier 1 capital ratio uses risk-weighted assets, while the Basel leverage ratio uses a separate leverage exposure measure.
• Accounting labels such as preferred stock or subordinated debt do not determine regulatory eligibility by themselves.

Tier 1 Capital Formula

Both components are measured after applicable regulatory adjustments.

Common Equity Tier 1 generally starts with qualifying common shares, related share premium, retained earnings, eligible reserves, and limited qualifying minority interests. Prudential deductions and filters then adjust that amount.

AT1 consists of instruments that meet the Basel eligibility criteria. At a high level, an eligible AT1 instrument must be:

• issued and paid in
• subordinated to depositors and general creditors
• perpetual, with no maturity date or incentive to redeem
• callable only under prescribed conditions, including supervisory approval
• able to have distributions cancelled at the issuer’s full discretion
• free of features that make cancelled distributions cumulative
• subject to the required loss-absorption treatment

Instrument terms and national implementation control the result. A security described in marketing material as “hybrid capital” or “preferred equity” may fail the regulatory test.

Worked Example

Assume a bank reports:

The same Tier 1 numerator produces different ratios because the denominators answer different questions.

CET1 and AT1 Compared

AT1 can strengthen the Tier 1 total, but it does not make the CET1 ratio higher. Analysts should therefore separate changes in common equity from changes caused by AT1 issuance, redemption, reclassification, or phase-out.

Tier 1 Compared With Tier 2

Adding Tier 2 to Tier 1 produces total regulatory capital. The capital categories should not be treated as economically interchangeable merely because each contributes to one regulatory total.

Why Tier 1 Capital Matters

Tier 1 capital is used in:

• the Tier 1 risk-based capital ratio
• the non-risk-based leverage ratio
• capital planning and stress testing
• distribution and redemption decisions
• large-exposure and other prudential limits
• regulatory filings and public capital disclosures

The Basel minimum Tier 1 risk-based ratio is 6% of RWA before applicable buffers and additional requirements. The Basel leverage-ratio minimum is 3%, but national rules, systemic-bank requirements, and bank-specific supervisory expectations can be higher or differently calibrated.

How to Analyze Tier 1 Capital

1. Reconcile CET1. Trace common equity, earnings, distributions, accumulated other comprehensive income, minority interests, deductions, and other adjustments.
2. Inventory AT1. Review each instrument’s principal amount, currency, call date, distribution terms, trigger or loss-absorption mechanics, and regulatory eligibility.
3. Check reporting scope. Consolidated group and regulated-subsidiary Tier 1 amounts can differ.
4. Identify transitions. Instruments can be phased out or lose recognition even while remaining outstanding.
5. Bridge period changes. Separate earnings and issuance from losses, dividends, redemptions, deductions, and foreign-exchange effects.
6. Review both ratios. RWA-based and leverage measures can impose different constraints.
7. Measure headroom. Compare reported ratios with all applicable minimums, buffers, surcharges, and internal targets.

Common Mistakes and Limitations

• Treating Tier 1 as only common stock and retained earnings.
• Assuming every perpetual preferred instrument qualifies as AT1.
• Treating a first call date as a maturity date or assuming the issuer will call the instrument.
• Comparing nominal AT1 issuance with regulatory recognition without checking adjustments and phase-outs.
• Reading the Tier 1 ratio without explaining RWA.
• Calling the leverage ratio a liquidity measure; it is a capital-to-exposure measure.
• Assuming strong Tier 1 capital guarantees solvency or liquidity under every stress.

Authoritative Sources

• Basel Framework CAP10: Definition of eligible capital
• Basel Framework CAP30: Regulatory adjustments
• Basel Framework RBC20: Minimum risk-based capital requirements
• Basel Framework LEV20: Leverage-ratio calculation

Related Terms

• Retained Earnings: Cumulative profits retained in the bank and included in CET1 subject to the capital rules.
• Tier 1 Capital Ratio: Tier 1 capital divided by RWA.
• Tier 1 Leverage Ratio: Tier 1 capital divided by the applicable leverage exposure measure.
• Capital Adequacy Ratio: The broader family of risk-based capital ratios.

Educational Use

This page provides general financial education, not investment, banking, accounting, legal, or regulatory advice. Verify current national rules and the exact instrument terms before assessing regulatory eligibility.