Decide Whether to Overpay Your Mortgage

You have a bit spare each month and the eternal question: overpay the mortgage or invest it instead. This runs the actual numbers, the guaranteed return from overpaying against the realistic return from investing, and checks your emergency fund first. You get a clear answer for your rate and balance, not a comment-section opinion.

<context>
You have a mortgage with {MORTGAGE_DETAILS} (rate, remaining term, balance). You have approximately {MONTHLY_SURPLUS} available each month that you could either put toward overpaying the mortgage or investing elsewhere. Your emergency fund is [adequate / not yet fully funded].
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<task>
**Make the overpay vs invest decision rigorously:**
1. Calculate the guaranteed return from overpaying (your mortgage rate) vs the expected return from investing
2. Factor in tax: mortgage interest relief (if applicable), ISA wrapper, basic vs higher rate taxpayer
3. Assess the liquidity difference: overpayments reduce flexibility; investments can be drawn down
4. Consider your psychological profile: does carrying debt cause you material stress?
5. Give a clear recommendation for your situation, with a monthly split if appropriate
</task>

<output_format>
- Rate comparison (mortgage rate vs realistic investment return after tax)
- Tax and wrapper impact (short paragraph)
- Liquidity trade-off (two sentences)
- Psychological factor note
- Recommendation with specific monthly split (e.g. 60% overpay / 40% invest)
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