When we researched the budget app-development category — the agencies that show up for "affordable app development company" — not one of them published a money-back guarantee. Reviews, portfolios and low rates, yes. A refund if the work misses the brief, no.
What ours actually covers
Two things: the $200 Starter Sprint, refunded in full if it doesn't match the written scope you approved before we started, and every individual milestone on a larger build — fixed free or refunded, your choice, if a signed-off milestone doesn't meet spec.
Why more agencies don't do this
A guarantee only works if your process produces a written, checkable scope in the first place. A lot of budget shops work off a verbal brief and a rough quote — nothing to hold a guarantee against. We write the scope down first specifically so a guarantee is possible.
Full terms, what's not covered, and exactly how to claim one: see the guarantee page.