Benfords law is not used to detect fraud. It is a tool used by forensic analysts to detect any anomalies or abnormal activity.

In accounting and finance there is something called "materiality", which is essentially a minimum threshold dollar amount used in auditing that is used to either dismiss something or investigate further. When auditing financial statements you compare the current year to the prior year, because the ratios and growth should be similar.

For example, if a company had $100,000 of expenses in year 1, but $1,000,000 of expenses in year 2 you would 100% go through each line item expense to understand why there was a 1000% increase.

But if in year 1 the company had $100,000 of expenses and in year 2 they had $110,000 of expenses you more than likely would not investigate too deeply because it is on par with the prior year.

Every client and every accounting book is different and has different materiality. It goes on a case by case basis.

It is little know that fraud actually increases every year and there is more financial fraud now than there was 10 years ago or 20 years ago. People get caught when they cross that materiality threshold and get people asking questions.