Frequently Asked Questions About Lewis Donnovan Monthly Budget Spreadsheet Method
22 answers covering everything from basics to advanced usage.
// Basics
What does zero-based budgeting actually mean?
Zero-based budgeting means every pound of income is deliberately assigned a job before the month begins, rather than spending first and saving whatever's left. In this method you allocate income across bills, savings, debt, and a personal allowance until Left to Allocate settles into the £150–200 buffer zone — so no money is left drifting unassigned.
Why do I confirm income before listing any outgoings?
Because you cannot allocate what you haven't counted. If you start with outgoings before locking your total income — net salary plus side income plus rollover buffer — the Left to Allocate figure is meaningless. Income-first sequencing ensures every allocation decision is made against a confirmed number, so you never accidentally plan to overspend.
What do the colours mean in the budget cells?
Each category cell signals its status by colour: white means exactly allocated and healthy, red means underallocated and dangerous because you haven't covered the cost, and green means overallocated with a surplus. The goal for most categories is white. Green is only acceptable — even desirable — on the personal allowance, where surplus just means extra spending money.
How long does this budget take to complete each month?
Under 30 minutes once your spreadsheet is set up. Most of the time goes into confirming income, counting food shopping days, and distributing pot savings across sinking funds. Because the categories and formulas stay the same month to month, you're mostly updating numbers rather than rebuilding the structure.
// How To
How do I calculate my food budget for the month?
Count the number of weekly shopping days between now and your next payday, then multiply by your weekly food spend (your half if split). Subtract shops for weeks you'll be away, add a small food emergency buffer of £10–20, and add a separate lunch allowance if you commute. Enter the total and confirm the cell turns white.
How do I distribute money across my sinking fund pots?
In your pots tab, split the month's total pot savings across each named pot — travel, car maintenance, Christmas, health, vet bills, birthdays — based on urgency and target balances. Prioritise pots with imminent needs; an upcoming holiday gets a heavier travel contribution. Record each balance so you can track progress month on month.
How do I set my personal allowance?
Choose a fixed amount — the same every month — that covers everything you spend on yourself for enjoyment. Lewis anchors his at £500, roughly 14% of income. Keep it consistent and never eliminate it to chase maximum savings. This cell is allowed to go green because surplus here just means more discretionary spending, which keeps the system sustainable.
How do I use 0% credit cards within this budget?
Use 0% interest credit cards as a timing tool, not debt: charge an expense that falls early in a month so you can pay it off in the intended budget month. Enter the payoff amount in your Debt Payments block. Keep zero-balance lines visible as a motivating record of debt cleared.
// Troubleshooting
My Left to Allocate is negative — what do I do?
Rejig the budget. A negative Left to Allocate means you're planning to spend more than you earn, which the system prohibits. Review each category and reduce one or more allocations — often the personal allowance or discretionary pot savings — until the figure returns to the £150–200 positive target zone before the month begins.
My Left to Allocate is way over £200 — is that bad?
It's not dangerous, but it means money is sitting unassigned and underused. Increase your savings or investment contributions, or top up pot savings toward their targets, rather than leaving the surplus to drift. The whole point of zero-based budgeting is giving every pound a job, so push the excess into something purposeful.
What if an unexpected cost hits mid-month?
That's what the rolling buffer and food emergency buffer are for. The £150–200 left in your account absorbs minor surprises without blowing the budget. For larger irregular costs, draw from the relevant sinking fund — a vet bill from the vet pot, for example — which is exactly why you ringfenced those pots in advance.
A bill cell is red — how do I fix it?
Red means underallocated — you haven't covered the full cost. Check whether a bill increased (a remortgage, council tax rise, or price hike) and update the amount you've entered so it matches the real cost. The cell turns white once the allocation covers the expense. Never leave a red cell going into the month.
What's the single most common mistake with this method?
Only budgeting when something goes wrong. The method works because it's done at the start of every single month, proactively — not reactively after an overspend. The other frequent mistakes are starting with outgoings before confirming income, and zeroing out the account instead of keeping the rolling buffer. Consistency is what makes it effective.
// Comparisons
How does this compare to just saving whatever's left at month-end?
Saving leftovers is reactive and inconsistent — most months little or nothing remains. This method flips it: savings and investments are allocated upfront as a deliberate category, and spending is capped by what's left afterward. That makes saving consistent and planned rather than an afterthought, which matters enormously for long-term goals like early retirement.
How is this different from a budgeting app like Monzo or YNAB?
Apps automate tracking but often give you less visibility into the logic. This spreadsheet method puts you in direct control of every allocation, shows colour-coded status at a glance, and includes UK-specific touches like TV licence, council tax splits, and annual-cost monthly budgeting. It shares YNAB's zero-based philosophy and sinking funds but costs nothing and is fully customisable.
How does the rolling buffer differ from an emergency fund?
The rolling buffer is a small amount (~£195) left in your current account each month as a first line of defence against minor surprises. An emergency fund is a separate, larger pot of savings for major events like job loss. The buffer handles small bumps without touching your emergency fund, keeping that intact for genuine crises.
Should I maximise savings or keep a big personal allowance?
Keep a meaningful personal allowance. The method's Balance vs. Maximisation principle holds that the goal isn't squeezing every penny into savings — it's living in the now while saving for the future. An allowance that makes life enjoyable is a feature, not a flaw, because a joyless budget gets abandoned. Sustainable beats aggressive.
// Advanced
How do I adapt the £150–200 buffer to a higher or lower income?
Scale it proportionally. The £150–200 target zone is calibrated to Lewis's £3,000 salary. On £2,500 you might aim for £100–150; on a much higher income you'd scale up accordingly. The principle is a small positive buffer relative to your income — enough to absorb surprises without leaving large sums unassigned.
How does bridge account thinking fit into early retirement planning?
A Stocks and Shares ISA acts as a bridge account — accessible money to fund the gap between your planned early retirement date and the age you can draw a pension. Contribute consistently and long-term. It lets you stop working before pension access by covering those bridge years, which is essential for anyone targeting FIRE in the UK.
How do I use the Outgoing Breakdown Wheel to sense-check my budget?
The wheel is a pie chart showing each category as a percentage of income. Check that fixed costs (bills, subscriptions, food, insurance) stay under about 50%, that savings and investments feel proportionate to your retirement timeline, and that your personal allowance sits around 14%. Compare these against frameworks like 50/30/20 to confirm your split is healthy.
Can I use this method if my income varies month to month?
Yes. Income-first sequencing is built for it — you confirm actual income (salary plus variable side income plus rollover buffer) before allocating, so each month's budget reflects reality. In leaner months, scale down flexible categories like personal allowance and pot savings. In stronger months, direct the extra into savings or pot top-ups rather than lifestyle creep.
How do I handle a month with a holiday in it?
Reduce your food block by subtracting the weeks you'll be away, keeping a small buffer for partial weeks on return. Direct a larger-than-normal amount into your Travel sinking fund for spending money abroad, and include any trip costs charged to a credit card in Debt Payments. The system absorbs the holiday by redistributing pot savings, not by overspending.