Clubs sometimes conclude deals at the last minute and it is not always easy for them to get everything completed and sent over by the deadline.
The deal sheet allows a club to confirm that a deal has been reached in order to allow for additional time to submit the remaining documentation.
For a deadline of 19:00, the deal sheet cannot be used before 17:00 and needs to arrive fully completed before the transfer window closes.
Once the sheet arrives, clubs have got another two hours, or until 21:00, in which to submit the full paperwork.