Tier 1 Capital

Tier 1 capital is the primary, highest-quality capital held by a bank, composed mainly of common stock (equity) and retained earnings. Under Basel capital standards, it is further divided into Common Equity Tier 1 (CET1) — the most loss-absorbing — and Additional Tier 1 (AT1) — like contingent convertible bonds that convert to equity in a crisis.

What constitutes Tier 1 capital

Common Equity Tier 1 (CET1):

• Common stock (ordinary shares).
• Retained earnings (accumulated profits not paid out).
• Disclosed reserves.

This is pure equity: holders are fully at risk and are paid last if the bank fails.

Additional Tier 1 (AT1):

• Contingent Convertible (CoCo) bonds.
• These are bonds that convert to equity if the bank’s capital falls below a trigger (e.g., if CET1 falls below 5.125%). They are hybrid instruments — debt until they convert, then equity.
• The conversion mechanism protects the bank: as losses mount, additional capital (from the converted bonds) automatically materialize.

Why Tier 1 is the first line of defense

When a bank suffers losses, they reduce capital. Tier 1 is the first to absorb losses because it is purely equity — nothing senior to it (except deposits and unsecured creditors, who are protected by deposit insurance and bankruptcy law).

Example: A bank has $100B in assets, $10B Tier 1 capital, $2B Tier 2 capital, $88B liabilities.

If losses are $5B:

• Assets fall to $95B.
• Tier 1 capital falls to $5B (absorbs the loss).
• Bank is still solvent; liabilities are covered.
• But capital ratio drops from 10% to 5%; regulatory warning.

If losses are $12B:

• Assets fall to $88B.
• Tier 1 capital falls to -$2B (negative!).
• Bank must also use Tier 2 capital ($2B).
• Still insolvent; depositors and creditors face losses.

The larger the Tier 1 capital, the more loss the bank can absorb before insolvency.

Basel III capital hierarchy

Under Basel III, capital is tiered by quality:

1. Common Equity Tier 1 (CET1): Most loss-absorbing. 4.5% minimum.
2. Additional Tier 1 (AT1): Hybrid; converts to equity in crisis. Combined with CET1, totals 6% minimum.
3. Tier 2: Subordinated debt and reserves. Combined with Tier 1, totals 8% minimum.

A bank prioritizes building CET1 because it is the highest-quality capital. Regulators require minimum CET1, not just total capital, to ensure the best quality buffer.

Capital buffers above Tier 1 minimum

Regulators require additional buffers above the 4.5% CET1 minimum:

• Capital conservation buffer: 2.5% above minimum. If CET1 falls below 7% (4.5% + 2.5%), the bank must restrict distributions (dividends, share buybacks).
• Counter-cyclical buffer: 0-2.5% (discretionary). Regulators raise this in boom times, releasing it in downturns.
• G-SIB surcharge: 1-3.5% (for systemically important banks).

A large bank might need 10%+ CET1 to avoid distribution restrictions.

How banks build Tier 1 capital

1. Retain earnings. The simplest way: earn profits and do not pay them out. Retained earnings add to Tier 1.
2. Issue stock. Raise capital by selling new shares. Dilutes existing shareholders but increases Tier 1.
3. Issue AT1 bonds. Sell hybrid instruments. Cheaper than stock (lower coupon) because investors know they might convert to equity in a crisis.

Most banks prefer to retain earnings (capital is cheaper than raising it externally) and supplement with stock or AT1 when necessary.

Tier 1 capital and shareholder returns

There is a tension: Tier 1 capital reduces shareholder returns because:

• Tier 1 = capital held in reserve, not deployed to earn high returns.
• Higher Tier 1 means less leverage, lower returns on equity (ROE).

A bank with 10% Tier 1 capital has 10x leverage, so profits are leveraged 10x. A bank with 15% Tier 1 capital has 6.7x leverage, so profits are leveraged less.

Higher capital = lower ROE, all else equal. This is why some banks resist capital requirements; they reduce shareholder returns.

Regulators accept this trade-off. Safety (higher capital) is more important than maximum shareholder returns.

See also