What is the after-tax yield of keeping extra mortgage cash in savings?

✓ Accepted answer

The after-tax yield of keeping extra mortgage cash in savings is typically 1.5% to 2.5% in the US and 0.5% to 1.5% in the UK, significantly lower than the interest saved by paying down a high-rate mortgage.

• US High-Yield Savings Rates: As of 2025, top US digital banks offer 4.5% to 5.0% APY on savings. After federal and state income tax, the net yield drops by roughly 30% to 40%, leaving you with a realistic 2.8% to 3.5% after-tax return on parked cash.
• UK Savings Account Comparison: UK Current Account rates have risen to match 4% to 4.5% in 2025. For basic-rate taxpayers, the net yield is higher, around 3.0% to 3.4%, but the capital gains tax implications for large lump sums in investment accounts still apply.
• Mortgage Interest Differential: If you hold a US mortgage at 7% or a UK mortgage at 6.5%, the interest saved is tax-free. Paying down a $100,000 mortgage at 7% saves you $7,000 annually, whereas saving that $100,000 in a 4.5% US savings account yields only $4,500 pre-tax (or ~$2,800 after-tax).
• Opportunity Cost Analysis: For every $10,000 in extra cash, paying down a 7% US mortgage creates a guaranteed 7% return with zero tax liability. Keeping that cash in a 4.5% savings account creates a net return of only 2.8% after taxes. The gap is nearly 420 basis points annually.
• Liquidity Considerations: While mortgage prepayment reduces interest, it locks cash in equity. Ensure you maintain a 3-6 month emergency fund in liquid savings before making extra repayments, especially if you are close to retirement.

admin · 2026-10-09 13:28:18