Guide
Startup business plan: what to write, and what to prove
Most startup plans fail because they describe an intention rather than an argument. A plan is useful when someone can read it, see what has to be true for the business to work, and check whether it is.
How much can I spend to acquire a customer?
Your ceiling is the lower of two limits: what a customer is worth over their lifetime, and what you can afford to wait to earn back. Change any assumption and the answer updates.
Example: a $120/month service at 70% margin losing 4% of customers a month
You can spend up to $504 to acquire one customer. The cash payback limit sets this ceiling.
- Monthly contribution per customer
- $84
- Expected customer lifetime
- 25 months
- Lifetime contribution
- $2,100
- Ceiling from 3:1 lifetime value
- $700
- Ceiling from 6-month payback
- $504
- Maximum cost to acquire a customer
- $504
- Customers your acquisition cash covers
- 9
How this is calculated (v1.0.0)
- monthly contribution = price × gross margin
- lifetime = 1 ÷ monthly churn
- lifetime ceiling = monthly contribution × lifetime ÷ target LTV:CAC
- payback ceiling = monthly contribution × payback months
- ceiling = the lower of the two
- One-off sales: set churn to 100% and payback to 1 month to get a single-purchase ceiling.
- Margin should include delivery and payment costs, not only product cost.
Continuing carries these exact inputs and results into Business Ontology — 3 free runs, no account needed.
Start with the customer and the problem, not the idea
Write down who has the problem, how they handle it today, and what that costs them in money, time, or risk. If you cannot name the person and the moment the problem shows up, the rest of the plan has nothing to stand on.
Be specific enough to be wrong. "Small businesses" is not a customer. "Plumbing firms with three to ten vans who schedule by phone" is one you can go and talk to.
Define the offer as something someone can buy
State exactly what the buyer gets, what it costs, and what happens after they pay. A plan that stops at a product description leaves out the part that determines whether the business works: how the promise is delivered, repeatedly, at a cost you can survive.
- What is included, and what is explicitly not
- The price, and why the buyer would consider that fair
- What you have to do each time someone buys
- How long delivery takes and who does it
Put real numbers behind the story
Three numbers decide most early businesses: what it costs to get a customer, what that customer pays you over time, and what it costs you to serve them. Write each as an arithmetic line with your assumptions visible, so anyone can change one input and see what happens.
Then write down the break-even point. How many customers per month covers your costs? If the answer is uncomfortable, it is better to know it now than after you have spent the money.
Name the assumptions that would sink you
Every plan rests on a few beliefs that have not been tested. List them plainly — that buyers will pay this price, that you can reach them for this cost, that delivery takes this long — and rank them by how much damage a wrong answer would do.
The top of that list is your work queue. A plan that ends in a set of tests is a plan you can act on this week.
Turn the plan into the first thirty days
Convert each untested assumption into a concrete piece of work with an owner, a cost, and a result you would accept as evidence. Ten conversations with the exact customer you named. One priced offer put in front of them. One channel tried with a budget you can afford to lose.
Common questions
How long should a startup business plan be?
Long enough that the argument is complete and short enough that you will keep it current. The parts that matter are the customer, the offer, the numbers, and the assumptions being tested.
Do I need a business plan to get funding?
Investors and lenders usually ask for one, but what they read for is the reasoning and the evidence behind your numbers, not the formatting of the document.
How is this different from a business plan template?
A template gives you headings to fill in. Business Ontology works through the plan with you, keeps the numbers as arithmetic you can change, and turns the untested parts into work you can actually run.
Start with your own business
Describe what you are building and Business Ontology works through it with you — the plan, the numbers behind it, and the work that follows.