The One-Page Business Plan (And When You Actually Need a Long One)

Most business plans are written once, to feel prepared, and never opened again. That version is a ritual, not a tool.

A plan does exactly one useful thing: it makes your assumptions explicit, so reality can contradict them. Vague plans can never be proven wrong, which is precisely why they feel so comfortable to write.

One page does that. Forty pages usually doesn't, because nobody re-reads forty pages.

The seven things the page must contain

1. The customer — specifically

Not "small businesses." Not "millennials." A segment specific enough that you could list ten real examples by name.

Solo trades businesses in the UK doing £80k–£250k, no in-house admin, currently using a bookkeeper for reconciliation.

If you can't name ten, the segment is too broad to market to.

2. The problem, as they'd describe it

In their words, not yours. "Reconciliation eats a Sunday every month" beats "inefficient financial workflows." If you did the validation conversations, you already have this sentence — it came out of someone's mouth.

3. Your offer

What they get, stated as an outcome. One sentence. If it needs a paragraph, the offer isn't clear enough yet to sell.

4. Price

An actual number. "Depends on scope" is not a plan; it's a deferral. If pricing genuinely varies, write the range and the two variables that move it.

5. Delivery cost

What it costs you to deliver one unit — hours, materials, subcontractors, fees. This is the number people skip, and it's the one that determines whether the business works.

Price minus delivery cost is your contribution. Everything else in the business is paid for out of it.

6. The channel

One way you'll reach the customer, named specifically. Not "social media" but "posting in the three trade forums where they already ask about this."

One channel. New businesses spread across five and go deep on none.

7. What must be true in 90 days

The falsifiable part, and the most valuable line on the page:

By 30 November: 8 paying customers at £180/month, acquired through trade forums, with delivery under 3 hours each.

Now the plan can be wrong, which means it can teach you something.

The whole thing, assembled

CUSTOMER   Solo trades businesses, £80k–£250k, no in-house admin
PROBLEM    "Reconciliation eats a Sunday every month"
OFFER      Monthly reconciliation done for you, back within 48 hours
PRICE      £180/month
COST       ~2.5 hrs delivery (£75) + software £12  =  £87
           Contribution: £93/customer/month
CHANNEL    Three trade forums where they already discuss this
90 DAYS    8 paying customers, delivery under 3 hrs each, by 30 Nov

BIGGEST ASSUMPTION
  That they'll hand over receipt access to someone they haven't met.
  Test: offer the first month at half price to the first three.

That fits on an index card and it's enough to start. Note the last block — name your biggest assumption and how you'll test it. That single addition converts a plan from a statement of intent into an experiment.

Do the arithmetic once

Before you commit to the page, run the numbers to a target:

| | | |---|---:| | Income you need per year | £48,000 | | Contribution per customer per month | £93 | | Customers needed | 43 | | Delivery hours at 2.5 hrs each | 107 hrs/month |

Now you can see the business. Forty-three customers is a real number you can plan around. And 107 hours a month of delivery tells you when this stops being a one-person operation — which is a much more useful thing to know at the start than at the point it happens.

If the arithmetic produces an impossible number — a thousand customers, or more delivery hours than exist in a month — you have found a pricing or model problem while it's still free to fix.

When you genuinely need a long plan

Write a full document only when someone external requires one:

• A lender. Banks and SBA-style lenders have a required format and will ask for projections, collateral and personal financial detail.
• An investor. Different again — market size, competition, team, and a route to a return.
• A visa, grant or licensing application. These have prescribed formats. Follow them exactly.
• A co-founder agreement. Not a business plan as such, but the same discipline applied to equity, roles and what happens if someone leaves. Get that one reviewed by a lawyer — it's the document that matters most when a relationship goes wrong.

In every case the audience is external and the format is theirs, not yours. That's a different job from thinking clearly, and it should not be confused with it.

The mistakes

1. Writing it once. A plan you never revise is a record of what you believed before you knew anything.
2. Projecting five years. Nobody can forecast year three of a business that has no customers. Ninety days is the honest horizon.
3. Omitting delivery cost. Revenue plans without cost plans are wishes.
4. Vagueness as safety. "Growing market" and "high demand" can't be wrong, which makes them worthless.
5. Confusing the plan with the work. A month spent perfecting a document is a month not spent talking to customers.

Revise it monthly

Fifteen minutes, once a month, against your weekly review numbers:

• Which assumptions did reality contradict?
• Is the 90-day target still reachable? If not, what changed?
• Has the customer segment narrowed as you learned more? It usually should.

A plan that never changes means you either aren't learning or aren't looking.

What to do next

Write the seven lines today — it takes twenty minutes. Then look hard at the arithmetic. If the customer count you need is a number you can picture, you have a plan. If it isn't, you have found the thing to fix before anything else.