Offset Mortgage Calculator (UK 2026)
Calculate offset mortgage interest savings and reduced term by linking savings accounts to reduce mortgage interest charged.
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Offset Mortgage Guide
How Offset Mortgages Work?
Offset mortgage: links your savings account(s) with your mortgage. Mortgage interest is calculated only on (mortgage balance − offset savings balance). You can still access your savings — they remain liquid. Example: £200k mortgage, £30k savings linked. Interest charged on £170k, not £200k. Your savings effectively earn the mortgage interest rate — but without tax. £200k at 5.5%: interest £11,000/year. £170k at 5.5%: £9,350/year. Saving: £1,650/year just by linking savings.
What do I need to know about Tax Advantages?
Crucial benefit: offset 'earnings' are not taxed. Standard savings: 5% interest. Basic rate taxpayer: £100 interest × 0.80 = £80 net. Higher rate: × 0.60 = £60 net. Personal Savings Allowance: basic rate £1,000/year tax-free. Higher rate £500. Additional rate £0. Above PSA: pay tax at marginal rate. Offset interest equivalent: mortgage interest avoided is effectively pre-tax earnings. Higher-rate taxpayer with mortgage at 5.5%: equivalent gross savings rate = 5.5% / 0.6 = 9.17% to match what an offset mortgage effectively delivers tax-free, which is a meaningfully better deal than most standard savings accounts can offer after tax.
When Offset Pays Off?
Best for: higher-rate taxpayers (greater tax advantage). Variable savings (offset benefit increases as savings grow). Self-employed with VAT or tax savings (use these as temporary offset). Inheritance, bonuses, capital received — accessible while reducing interest. Worst for: low savings (offset rates typically slightly higher than non-offset). Building society members with linked products already getting bonus rates. Anyone needing maximum borrowing — offset products may have lower max LTV. Rates on offset mortgages are typically 0.25-0.5% higher than an equivalent standard mortgage, so the savings-rate benefit needs to outweigh this premium to be worthwhile.
What do I need to know about Offset Provider Considerations?
Major UK offset lenders: First Direct (uses overdraft-style flexibility). Yorkshire BS (Offset mortgage, flexible). Family Building Society (Offset). Scottish Widows. Coventry BS. Each has different rules — read carefully: some allow multiple offset accounts. Some restrict to 1-2 accounts. Some allow joint account offset. Some only single named account. Some include current account offset. Most are linked savings only. Overpayment rules: offset mortgages typically very flexible. Overpay any amount at any time without penalty, since the linked savings simply act as an offset rather than a formal overpayment against the loan.