FREE TOOL SCOPE — invoicing product

PICK THE ONE WITH SEARCH INTENT THAT MATCHES YOUR PRODUCT
Ranked by how close the searcher is to needing what you sell:

  Invoice generator           Vol ~40K/mo · Difficulty HIGH · Intent ★★★
    Highest volume, most competitive, and the searcher wants exactly
    what you do. Crowded but correct.
  Late fee calculator         Vol ~3K/mo  · Difficulty LOW  · Intent ★★★
    ← RECOMMENDED. Whoever searches this has unpaid invoices right now.
    That's your customer at the exact moment of pain, and the SERP is
    winnable in a quarter.
  Freelance rate calculator   Vol ~12K/mo · Difficulty MED  · Intent ★
    Great traffic, wrong person. They're deciding what to charge, not
    struggling to collect. Links yes, signups no.

BUILD SPEC — late fee calculator
  Inputs   invoice amount · due date · terms (net 30/60/custom) ·
           jurisdiction (statutory max varies)
  Output   interest owed to date · daily accrual · the legally
           permissible max in that jurisdiction
  ← the jurisdiction piece is the moat. Every competing calculator does
    flat percentage math; none handle statutory caps, and that's the
    part people actually search for.

THE THREE RULES
  1. No email gate on the result. Gating kills the sharing that earns
     the links, and links are the whole point.
  2. Result page is the CTA surface: "Send this as a reminder →" leads
     into the product at the moment of intent.
  3. Shareable URL that encodes the inputs. Every share is a backlink
     and a referral.

WHAT SUCCESS LOOKS LIKE
  Month 3   ranking top 10, 400 sessions/mo
  Month 6   top 3, 2K sessions/mo, 3–5% tool-to-signup
  Month 12  the calculator outranks your homepage for its term and
            feeds the blog cluster around it

  2K/mo at 4% is 80 signups — modest, but they arrive with an unpaid
  invoice in hand. Judge it on signup quality, not traffic.