Feature spec
Goal: Send a clear invoice after finishing a job.
- Add a client, line items, a due date, and payment instructions.
- Preview the total before exporting a PDF.
- Keep an editable draft if export fails.
App Overview
Tax It - Sales Tax Calculator
NEW VERSION 13.0
$1.99 · In-app purchases
PRICE
$1.99
In-app purchases
BUSINESS MODEL
Paid
No overall Grossing estimate available
RATING
★ 4.0
1 ratings · Top 30%
Evidence scope: No current overall US chart position is available. Category-chart positions shown in discovery are a separate scope. Revenue is a directional model estimate, not verified earnings.
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Build Kit
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A product spec, screen plans, and build steps for your coding agent.
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What's included14 files
A product spec, phased build plan, differentiation notes, and screen references.
- START_HERE
- AGENTS
- EVIDENCE
- SPEC
- BUILD_PLAN
- DIFFERENTIATION
- skills/
- screens/
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Illustrative example: an invoice app for independent contractors. Your kit is tailored to the app you choose; this is not its generated content.
Screen plan
Invoice editor: Client at the top, editable line items in the middle, total and preview action at the bottom.
States: Empty draft, validation errors beside each field, exporting, and a retry action that preserves the draft.
Differentiate and validate
Hypothesis: Contractors need faster repeat invoices more than more templates.
First experiment: Test duplicating a previous job with five contractors. Watch where they hesitate before expanding the feature set.
The full kit adds a phased build plan, evidence notes, tool prompts, and implementation guidance. It is a plan for your coding agent, not a finished app.
Usage: Mechanics are fair game; never reuse the original name, branding, assets, or verbatim copy.
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Free quick prompt For a smaller starting point
Quick prompt
Good fit for mobile-first iOS and Android prototypes with managed app scaffolding.
// RORK SYSTEM PROMPT
Rork plan preview for Tax It - Sales Tax Calculator: map the core Finance workflow, choose the smallest differentiated feature set, define the data and monetization boundaries, then prototype the riskiest user journey first.
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Opportunities
AI-GENERATED OPPORTUNITY HYPOTHESES
These are generated suggestions, not verified review quotations. Check current App Store reviews and speak with users before treating a possible gap as a requirement.
Hypothesis 1
Offer additional finance tools like budgeting or expense tracking.
Assumption to check: Limited features compared to full accounting apps
Validate with people who use this workflow before building.
Hypothesis 2
Introduce features for recurring tax calculations.
Assumption to check: Single-purpose app may not retain users
Validate with people who use this workflow before building.
Hypothesis 3
Implement CSV export for calculation history.
Assumption to check: No data export options
Validate with people who use this workflow before building.
Hypothesis 4
Allow users to set preferred tax rates and save them.
Assumption to check: Lack of user customization options
Validate with people who use this workflow before building.
App evidence
Original App Store material. Ratings and screenshots describe the existing app, not proof of demand for your version.
App Store description
NEW VERSION 13.0 Tax It is an all in one Sales Tax, Discount and Tip Calculator Set your tax rates, discount percent and tip percent in the convenient slide out option screen, just swipe right. Ever wondered what your total purchase would be with sales tax? Maybe they are offering a discount and you'd like to know what that total would be...then you'd like to add sales tax to that. Well now you can with Tax It. At a restaurant and need a fast way to figure out a tip? No Problem there's an app for that and it is Tax It. With the Round Tip option it will round your total to the nearest highest dollar. Copy and Paste numbers into the calculator * Includes restaurant tax button for those who live in areas with a different tax rate for prepared food. * Will only calculate up to 2 decimal places. Calculator will round number with more than 2
Written user reviews are not shown here. Check current App Store reviews >
Screenshots
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Build scope
Plan a focused first version with your coding agent. These are planning assumptions, not a delivery guarantee.
Define the first version
Choose one audience and one core workflow. Use the kit to agree on its screens, data, and acceptance criteria before building.
Set boundaries
Decide which secondary features, integrations, and platform support can wait. Your version does not need to reproduce everything in the original.
Check the hard parts
Validate external services, specialist technology, data access, and ongoing costs for your chosen scope.
SUGGESTED BUILD STACK
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BUILD KIT DIFFICULTY
Starter
From the Build Kit assessment.
A reliable timeline needs an agreed scope and a technical check. Ask your agent to estimate the phases in BUILD_PLAN.md after that review.
