The state rule, the city rule, and the one that follows your debtor

Sometimes - it depends on your contract and state law. Where your terms and conditions provide for collection costs and interest, and the applicable state permits it, those amounts may be added to the claim. That clause is worth having in your standard terms before you need it; ask your counsel to review it.

No. The Fair Debt Collection Practices Act defines 'debt' as an obligation of a consumer arising out of a transaction primarily for personal, family or household purposes - business-to-business obligations fall outside the statute entirely. That does not mean B2B collection is unregulated: state collection statutes, phone-consent rules, contract terms and ordinary law still apply.

An agency works your account for a share of what it recovers and returns what it cannot collect - you keep ownership of the debt. A debt buyer purchases the account outright, usually for cents on the dollar, and keeps everything it recovers. For unpaid B2B invoices where the customer relationship may be salvageable, the agency model is normally what businesses want.

It depends on the state - 31 jurisdictions require a licence or registration, Texas requires only a $10,000 bond filed with the Secretary of State, and the rest require neither. The rule that surprises creditors is that several states look at where the debtor is located, so a multi-state ledger can require an agency licensed in states you never thought about.

Commercial collection is normally contingency-based - a share of what is actually recovered, commonly 10-40%. Account age drives the rate more than balance size: fresh accounts under 90 days commonly run 10-25%, 90-180 days 15-30%, 180 days to a year 20-35%, and over a year 25-40%. Some agencies also offer fixed-fee early-stage demands at roughly 15-20 dollars per account.