Good morning Graham Light,
Nice to see you in the QuickBooks Community! As long as you have followed all the steps in this checklist I am attaching below, you are good to close your books.
Please note that closing your books will prevent you from making changes to any transactions on or before the closing date. Once you have reviewed the guide and are ready to close, this link (which includes a video presentation) will instruct you on how to do so and prepare for the new year.
If you have any questions as you go through the checklist, feel free to let me know! I will be here to assist you further. I hope you have a good day!