Some deals are already done – West Ham have signed Croatia forward Nikola Vlasic on a five-year deal this morning – while others are close.
These include Everton striker Moise Kean returning to Juventus on a two-year loan, while Cristiano Ronaldo’s move from Juve back to Manchester United will be confirmed later today.
The clock is ticking and so here is a definitive guide to deadline day...
When does the transfer window close?
The window will close at 11pm BST on August 31.
That date will vary from country to country, with some markets open for longer.
In that scenario, it would still be possible for players to leave English clubs, but those sides would not be able to bring in replacements.
What are deal sheets?
Sometimes clubs conclude deals at the very last minute, and it can mean that they struggle to properly sign off on the relevant paperwork before the 11pm deadline.
A deal sheet allows a club to confirm that an agreement has been reached in order to allow for additional time to submit the remaining documentation.
For tonight’s deadline of 11pm, the deal sheet cannot be used before 9pm, and must arrive fully completed BEFORE the transfer window closes.
Once the sheet arrives, clubs have an additional two hours, or until 1am, in which to submit the full paperwork.
When does the January transfer window open?
The next transfer window will open on Saturday, January 1, and close at 11.59pm on Monday, January 31, 2022.
The January window for La Liga and Serie A opens on January 3, but also closes on January 31.