In the United States, trade marks can be based either on actual use in commerce or a bona fide intention to use the trademark. The latter application is often called an ITU trademark application and is essentially a placeholder. The trademark will not actually be registered until the applicant files Statement of Use with evidence of the use of the trademark in the United States.
The requirements for the evidence of use are similar to those requirements needed to renew a registered US trademark. Basically, anything showing the evidence of use in the United States can be filed. This includes invoices, catalogues, photographs of products, or extracts from websites showing the goods or services. The evidence should be filed within six months of allowance of the trademark. This deadline can be extended up to five times on payment of a fee. Effectively, an applicant has three years from the date of allowance of the trademark to start using the mark in the US.
The fee for extending the deadline is currently (November 2020) USD 125 per class of goods.