Mistake one: the wrong version of the paper
The commonest refusal has nothing to do with America. The stamping office matches a signature on the page against a sample lodged with it, so a page carrying no such signature cannot be handled at all. Keepsake certificates, printed emails and home photocopies all fall into that group. Getting a certified extract from Edinburgh Registration Service instead removes this problem entirely and costs far less than a failed run.
Mistake two: notarising in the wrong country
American processes lean heavily on notaries, and it is a natural instinct to reach for one. The chain here does not work that way. Whatever is added to the page must come from a signer whose sample the British office holds. Anything applied abroad sits outside that check and adds cost without adding standing, however carefully it is done.
Mistake three: tidying up the stamped page
A stamped bundle is meant to arrive exactly as it left. People trim it to fit a folder, unstaple it to scan it, or laminate it for safe keeping, and each of those makes the slip harder to trust. Document legalisation for United States readers survives a plain envelope far better than it survives being tidied. Scan it whole if you need a file copy, then leave it alone.
Mistake four: paying twice for one job
The charge is £45 for each paper by post, or £40 for each paper on the next-day route open to registered firms. Doing several papers at once does not lower that per-paper fee, but discovering a missed paper afterwards means paying the postage and the waiting all over again. Listing every paper the American reader asked for, once and in writing, is the cheapest step in the whole exercise.
What the American reader actually checks
The reader is checking that a recognisable authority vouched for the signature, and that the page in front of them is whole. They are not reading the British process. American offices work in English, so a translator is rarely involved, which is why condition and completeness carry so much of the weight on this particular route.