On my bill for my Sprint mobile broadband modem, the “amount enclosed” portion of the form is rendered in the one-box-per-digit mode common to standardized forms. Observe, if you will, their presentation:

Under what circumstances, I wonder, would any of the places beyond the thousands get used? I can imagine an actual bill getting sent, to be remitted by check, that extends to a few thousand — I even know people who’ve done this with international roaming, knocking on the door of five figures. Bills greater than ten large, though, are almost certainly all handled by some sort of corporate billing and remittance mechanism. How often does Sprint really get some human filling out this form with 6 or 7 digits?