In most cases, it is legal for a business to refuse to take large bills, as they have the right to set their own policies regarding payment. However, there are some important factors to consider when it comes to the legality of refusing large bills.

Firstly, it is important to note that in most countries, including the United States, there is no legal requirement for businesses to accept any specific form of payment, including cash. Businesses have the right to set their own policies regarding payment methods and may choose to refuse large bills for a variety of reasons.

However, there are some exceptions to this rule. In some cases, refusing large bills could be considered discriminatory if it disproportionately affects certain groups of people, such as those who are low-income or rely on cash for their daily transactions. This could potentially violate anti-discrimination laws and lead to legal consequences for the business.

Additionally, businesses that are considered "public accommodations," such as restaurants, hotels, and other establishments that are open to the public, may be subject to different regulations regarding payment. For example, the Americans with Disabilities Act (ADA) requires businesses to provide equal access to goods and services to individuals with disabilities, which could include accepting certain forms of payment.

Another factor to consider is whether the refusal of large bills is related to potential money laundering or fraud concerns. In some cases, businesses may refuse large bills as a way to protect themselves from accepting counterfeit or fraudulent money. While this is not necessarily illegal, businesses should be careful to avoid discriminating against certain customers based on their perceived likelihood of engaging in fraudulent behavior.

In conclusion, while it is generally legal for businesses to refuse to take large bills, there are some important factors to consider, such as potential discrimination, accessibility, and fraud concerns. Businesses should be aware of their legal obligations and avoid any practices that could be viewed as discriminatory or illegal.