Transposition error
Recording $540 as $450 is a transposition. If it happens on one side only, the trial-balance difference is divisible by 9.
Example
$720 vs $270: difference $450 = 9 × 50.
Learn and practice it
Finding trial-balance differences — Use the size of a difference — the amount, double the amount, or a multiple of 9 — to locate errors fast.
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