Who hurts
Freelancers and contractors in their first three years of self-employment.
The problem
Income is lumpy, tax is owed quarterly, and the first year almost always ends in a bill that arrives after the money is gone.
What you build
Connect the business account, classify income and deductible expenses continuously, and show one number: set aside this much, this month. Plus the quarterly filing prep when it's due.
Why now
Expense classification is the only genuinely hard part, and it stopped being hard. The rest is careful, jurisdiction-specific arithmetic.
Validate it this week
One country, one filing status. Build the calculator as a free web tool first and see how many people return in the second quarter.
Why you'd keep winning
Jurisdiction depth and being trusted with the account connection. Both are slow, and slow is the point.
The honest risk
Wrong tax advice is a liability event and rules change annually. This is a maintenance business as much as a product business.
The prompt is written to make an AI argue with you before it writes code — that first round of pushback is worth more than the scaffold.