noun
statement of account; bill; invoice
A formal written document detailing charges, fees, or account activity, often used in business or official contexts.
月末にクレジットカードの計算書が届いた。
The credit card statement arrived at the end of the month.
取引先に計算書を送付してください。
Please send the statement of account to the client.
明細書 is a detailed breakdown or specification sheet, often itemized, whereas 計算書 focuses on the calculated totals or account summary.
Compound of 計算 (calculation) + 書 (document). The meaning is transparent from its components.