Final answer:
A significant decrease in the number of days' sales in accounts receivable generally indicates improved efficiency in collecting receivables. The assertion potentially violated would likely be Valuation or allocation, suggesting the receivables might be overstated or improperly valued.
Step-by-step explanation:
If the number of days' sales in accounts receivable (365 days/receivables turnover) decreases significantly, it most likely indicates that the company is collecting its receivables more quickly. This might suggest improved efficiency in managing receivables or changes in credit policies, rather than a violation of assertions related to accounts receivable. However, if we need to consider which assertion could be violated as per the question, the most likely assertion to be concerned would be Valuation or allocation. This is because a significant decrease in the days' sales in receivables may indicate that the receivables could be overstated or not properly valued, especially if sales are recorded correctly but the actual collection does not correspond to the recorded accounts. Thus, the valuation aspect, which involves ensuring that receivables are recorded at the appropriate value, might be compromised.