Budget vs Actual — The Two Numbers That Make a Budget Work

A budget with one number is a wish. The moment you put what you planned next to what happened, it becomes something you can actually steer by.

Most people who say budgeting does not work for them have done the same thing: written down what they intend to spend, felt organised for a week, and then never compared it to anything. The plan sits in a spreadsheet. Real life happens somewhere else entirely. The two never meet.

Businesses solved this problem decades ago and gave it a dull name. Variance analysis. Every finance department on earth runs the same simple comparison every month — what we said we would spend, what we actually spent, and the difference between them. The difference is the whole point. It is the only part that tells you anything.

Why one number is not enough

Say you plan to spend £400 a month on groceries. At the end of the month you have spent £480.

With only the plan, you have a target you have vaguely failed. With only the actual, you have a fact with no meaning attached — is £480 good or bad? You cannot tell.

With both, you have something specific: you are twenty percent over on groceries, that is £80, and £80 a month is £960 a year. Now it is a decision rather than a vague feeling of having overspent.

The difference is where every useful question lives. Was the plan wrong, or was the spending wrong? Both are fixable, but they need opposite responses, and you cannot tell which one you are looking at without the two numbers side by side.

The direction of good is not the same everywhere

This trips people up more than anything else, and it is the reason generic tracking apps feel slightly wrong.

For expenses, spending less than planned is good. Under is green.

For income, spending — earning — less than planned is bad. Under is red.

For savings, putting aside less than you planned is bad. Under is red again.

An app that colours every shortfall green because "less is good" will cheerfully congratulate you for saving nothing this month. When you set up your own tracking, whether in a spreadsheet or an app, check that it understands the difference. It sounds trivial. It changes what the numbers tell you.

Work in lines, not categories

Here is the mistake that makes budgets useless: planning at the category level.

You set £120 for subscriptions. At the end of the month you have spent £147. You are £27 over — but over on what? You have no idea, and so you cannot act. Next month you set £150, spend £163, and repeat forever. The budget is tracking your spending rather than governing it.

Now do it as lines:

Suddenly the £27 has a name. Spotify raised its price by three pounds. And cloud storage is nineteen pounds over because you are paying for two services — one you set up years ago and forgot, one that came with your phone.

Neither of those is a discipline problem. Neither would have been visible at category level. Both are solved in about five minutes once you can see them.

The plan should be a forecast, not a target

There is a persistent idea that a budget is an act of willpower — that you write down a small number and then heroically live within it.

That approach fails predictably, because the number was never realistic and everyone involved knew it. If you have spent £480 on groceries every month for a year, planning £350 is not ambition. It is fiction, and it will produce a red line every single month until you stop looking.

Start by planning what actually happens. Look at three months of statements, take the typical figure, and write that down. Your first month should mostly show differences near zero. That is not failure — that is a working model of your life, which is the thing you need before you can change anything.

Then change one line deliberately. Not eight. One. Move groceries from £480 to £430 and see whether it holds. A budget that describes reality accurately is worth more than one that describes an ideal you will abandon by the fourteenth.

What the difference column is telling you

After two or three months, patterns emerge, and they fall into a small number of types.

Consistently over on the same line. The plan is wrong, not you. Raise it and take the money from somewhere you genuinely do not care about.

Wildly variable month to month. This is usually a category that is really several things wearing one label. "Shopping" hiding clothes, gifts and household items. Split it into separate lines and the variability usually resolves into one volatile line and several stable ones.

A line that only ever drifts upward. Subscriptions, insurance, utilities. Nothing you did caused this. These are the ones to renegotiate rather than economise on.

Under by a lot, every month. Either you have stopped using something you are still paying for, or the plan was padded. Both worth knowing.

Doing it without much effort

The honest obstacle is not understanding — it is that filling in the actual column is tedious, and tedious things stop happening around week three.

Three things make it survive.

Import rather than type. Export a CSV from your bank and let something else read it. Most transactions can be sorted automatically, and you only correct the ones it gets wrong.

Plan once, not monthly. Copy last month's lines forward with their planned figures and leave the actuals blank. Ninety percent of your budget is the same every month.

Look weekly, not daily. Daily is obsessive and burns people out. Monthly is too late to change anything. Once a week, five minutes.

Putting it into practice

You can do all of this in a spreadsheet, and plenty of people do. Two columns per line, a difference column, a total row. It works.

What a spreadsheet will not do is warn you when a subscription price rises, or tell you that the service you are paying £17.99 for has a £7.99 tier that would do the same job.

Under the Mark is built specifically around this method — every line carries its own planned and actual figure, the direction of good is correct for income, expenses and savings separately, and it flags where you could pay less for things you already have. It is free, needs no account, and your figures stay in your browser.

If you are ready to start, our guide to downloading your bank statement as a CSV covers the first step for the ten most common banks.