It is a common explanation that there are samples on invoices, which usually means that samples of goods or services have been provided and invoices have been issued, and consumers can confirm that the goods or services received are consistent with the samples. Marking samples on invoices helps to protect consumers' rights and interests and avoid disputes arising from receiving goods or services that are inconsistent with the samples.

In some industries, samples on invoices can also indicate some additional benefits or rewards. For example, when buying some luxury goods or high-end goods, merchants may mark samples on invoices and attach specific preferential contents or gifts to attract consumers to buy more actively.

It should be noted that in some illegal or fraudulent transactions, there may also be sample instructions on the invoice. Therefore, consumers need to be cautious about such labeling, pay attention to verifying the authenticity of goods or services, and contact merchants or relevant departments to protect their rights in time when encountering problems. At the same time, we also need to actively learn and understand the relevant consumer rights and legal provisions in order to better protect our rights and interests.