Some of the biggest deals completed this month could be contract renewals for a number of big-name players.
England’s Georgia Stanway, 26, has attracted lots of attention, with Arsenal among those to have held talks with the midfielder. Her deal at Bayern Munich ends in the summer, and while she has an offer to extend, she could sign a pre-contract agreement in January to join another club in the summer.
Another England midfielder, Ella Toone, is out of contract at Manchester United in July. She can begin talks with other clubs outside the WSL this month.
Manchester City top scorer Khadija Shaw, 28, has had positive discussions over a contract extension, which is a huge priority for the club.
European champions Arsenal want to keep US international Emily Fox and she joins Katie McCabe, Kim Little and Stina Blackstenius in having a deal that expires this summer.
Chelsea are also due to hold negotiations with just six months remaining on the contracts of senior players Sam Kerr, Millie Bright and Lucy Bronze.
Aston Villa captain Rachel Daly is also out of contract in the summer, but will the club offer a new deal to the 34-year-old?
Elsewhere, Everton forward Kelly Gago, 27 on 5 January, has reportedly attracted interest from Paris St-Germain but with a valuation of £500,000, can the Toffees keep hold of her?
All eyes will be on US striker Trinity Rodman, who could be on the move from Washington Spirit depending on the outcome of salary negotiations with the National Women’s Soccer League (NWSL).
Chelsea are among those tracking Rodman’s situation, while Japan midfielder Maika Hamano could leave the Blues to join Tottenham on loan. US forward Catarina Macario also has interest from the NWSL, while Germany midfielder Sjoeke Nusken could seek more game time elsewhere.
Reports suggest West Ham might have to fend off interest in England defender Anouk Denton, while Amber Tysiak previously attracted suitors in the summer.