If you purchased a commercial subscription inside your Bitrix24 account, you can find your invoice here: Subscription > Purchase History.
By default, the Purchase History page is available only to the account administrators. Other users will have access to the Purchase History page if the Enable all users to upgrade current Bitrix24 plan option is enabled in the account settings.
If you purchased a commercial subscription from a Bitrix Partner (Bitrix Reseller), please request your invoice from your original Bitrix Partner.
If you purchased a commercial subscription and/or paid for a service inside an app from Bitrix24.Market, please get in touch with the corresponding app developer.
If you are having any difficulties finding your invoice, or have any questions regarding your payments, please get in touch with our Sales team in the support chat.