From your first payslip to your last pension drawdown — mapped in one spreadsheet.
Payslip to Payback is a free, open Excel workbook that models your entire UK financial life: income, tax, National Insurance, pension growth, ISA strategy, and retirement drawdown — all in one place.
This is a personal experiment, not financial advice. It can be wrong. Use it for curiosity only.
What It Does
Lifetime Projection
Model your finances from today through retirement and into drawdown. See how decisions made now ripple forward across decades.
Tax & NI Modelling
Built on 2025/26 HMRC rates for England. Income tax bands, National Insurance, personal allowance taper — all pre-loaded and overridable.
Pension Intelligence
Tracks Annual Allowance (including tapered allowance), employer contributions, and Safe Harbour rules. Models both accumulation and drawdown phases.
ISA & Wrapper Strategy
Compares S&S ISA, Cash ISA, GIA, SIPP, and workplace pension wrappers side-by-side to surface tax-efficient allocation choices.
Live Market Data
Pulls real-time data from the Bank of England and ECB APIs — base rate, gilt yields, exchange rates — directly into the model.
AI Tax Refresh
Optional Gemini API integration auto-refreshes key tax parameters when rates change. Requires a free Google AI Studio key.
Who might find this useful?
This tool is for people who like to understand their money, not just look at it. If you've ever wondered how much your pension is actually worth in today's money, whether your employer contribution is doing much, or what happens to your ISA if you take a career break — this is the kind of model that lets you poke around and find out. It's particularly useful for UK employees aged roughly 25–55 who want a single coherent picture, rather than a dozen disconnected apps.
Get started in about 5 minutes
- 1
Download the .xlsm file — it's a macro-enabled Excel workbook, ready to open
- 2
Enable macros when prompted — Excel will ask on first open; the macros handle data refresh and navigation. As far as we know, there is nothing malicious in this file — but you should make your own judgement, and we make no guarantees
- 3
Fill in the Start Here sheet — salary, age, pension contributions, and a few preferences
- 4
Hit Refresh All Market Data to pull in live rates from the Bank of England and ECB
- 5
Explore your projections across the 21 modelling sheets — adjust assumptions freely
Your data never leaves your spreadsheet
Payslip to Payback does not collect, transmit, or store any of your personal or financial data. Everything you enter stays inside the copy of the workbook saved on your own machine. The only outbound connections the workbook makes are to fetch market data from public APIs (Bank of England, ECB, and optionally Google Gemini for tax refresh) — none of which receive any of your personal inputs.
Download
Both files are provided free of charge, as-is, for personal use and experimentation. No account. No email. No tracking.
The requirements document describes what was built and why — useful if you want to understand the model's logic or limitations before diving in.
Help Tip: Opening the .xlsm file
What is a macro? A macro is a small program embedded inside an Excel file that automates tasks — in this case, fetching live market data and running the projection calculations. The .xlsm file extension means the workbook contains macros written in VBA (Visual Basic for Applications).
Why does Excel warn me? Because macros can run code on your computer, Excel disables them by default as a security precaution. This is sensible — you should never enable macros in a file you don't trust. The warning exists to protect you from potentially malicious files.
How to enable macros so the workbook works:
- Open the downloaded
.xlsmfile in Excel. You will see a yellow security banner at the top of the window saying "Macros have been disabled." - Click Enable Content on that banner. Excel will add the file to its trusted documents so you won't be asked again for this file.
- If you don't see the banner, go to File → Options → Trust Center → Trust Center Settings → Macro Settings and select "Disable all macros with notification", then reopen the file.
On macOS, the flow is similar: open the file, click Enable Macros when prompted. If macros are blocked, go to Excel → Settings → Security & Privacy and ensure macro notifications are enabled.
Please read this
Payslip to Payback is an experiment, not a financial product.
This workbook is shared for curiosity and personal exploration only. It is not regulated financial advice, and it does not constitute a recommendation to make any investment, pension, tax, or financial decision.
The projections it produces can be wrong — due to modelling simplifications, data errors, out-of-date rates, or inputs that don't reflect your actual circumstances. HMRC rules are complex and change frequently. This tool makes assumptions that may not apply to you.
Do not rely on this tool for retirement planning, tax filing, pension decisions, or any consequential financial choice without consulting a qualified financial adviser, accountant, or pension specialist.
Regarding macros: Excel will prompt you to enable macros on first open. We have no reason to believe the file contains anything harmful, but we are not security researchers, we cannot guarantee it, and you should make your own judgement before enabling macros on any file from the internet.
This software is provided without warranty of any kind, without support, and without any obligation to maintain or update it. Use it entirely at your own risk.