Money planning
A simple expense log for a side project
By You Me and Money · November 1, 2026 · Original practical guide
Separate fixed and variable costs
Fixed costs support the project regardless of the number of sales, such as a recurring tool subscription. Variable costs increase with each sale or task. Record the date, supplier, description, amount, currency, and purpose of each expense. This operational log does not replace records required for accounting or tax purposes.
Record commitments as well as payments
A trial that renews next month can affect the budget even before a charge appears. Note the renewal date, cancellation route, and which task the tool supports. Put related one-time purchases in the same review. Avoid keeping several tools that do the same job simply because each one seemed inexpensive when purchased.
Review a worked example
Suppose your monthly tools cost 30 and you spend 90 preparing a project. With an illustrative contribution of 15 per sale, eight sales would cover those entered first-month costs. That calculation does not predict demand or include expenses you forgot. Use our break-even and pricing tools to explore assumptions, then replace them with actual receipts and costs.
Choose a useful review rhythm
Review the log at a regular interval that fits the project. Ask which expense helped produce a usable deliverable and which can be paused. Keep personal finances and business decisions clear, and obtain qualified advice when you need it. The purpose of the log is visibility, not an invented profit target.