A quote clearly states its validity period when the document explicitly includes a field such as “Validity period for quotation” and gives the applicable date or date range. The U.S. International Trade Administration lists that phrase among quotation details. The cited guidance does not prescribe a universal number of days or one expiry-date format.
How to check the document
Look for a heading, label, or line that expressly identifies how long the quotation remains valid. A price, issue date, or general order description alone does not answer that question.
The cited guidance on pro forma invoices says that a pro forma invoice should give the buyer as much information about the order as possible so arrangements can be made efficiently. That is useful for checking whether the transaction is described clearly, but it is not the same as finding an explicit validity period for a quotation.
What to confirm before relying on it
Check the exact start and end dates, or the stated duration. Also read any wording that limits the period or makes it depend on stated conditions. If the validity field is missing or ambiguous, the issuer should confirm the period in writing rather than the reader inferring it from other order details.