This year the deadline falls at 7pm on September 1, with that the cut-off until player trading recommences in the new year.
As ever, it’s been a summer where names have come thick and fast in connection with Pompey.
Some of those reported talks, some have gone on to sign for the Blues with others, well, carrying less substance.
We’ve kept our ears to the ground, so here’s every player linked with Pompey so far - with some insight into the credibility of those reports.
5. Abdoulie Manneh
Pompey were keen but Gambian was expected to move to one of the continent's bigger clubs - but is still with Swedish side Mjallby. | Getty Images
7. Hector Kyprianou
The midfielder is admired by John Mousinho, but not a deal that was ever realistically on the cards - as underlined by Watford pushing the boat out to land Kyprianou on a five-year deal. | Getty Images
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8. Rob Atkinson
Wanted by Pompey and open to a Fratton move, but instead signed a new deal with Bristol City. | The News