I know the importance of having the correct month in filing your report. I can guide you on how to fix it.
Is your bank connected to your QuickBooks Self-Employed(QBSE) account? If so, the date displayed on the downloaded transaction comes directly from your bank. There may be a delay in your bank posting date.
As a workaround, you can exclude those transactions. Then, manually add or import them so they'll reflect the correct month.
Here's how:
Go to the Transactions menu.
Locate and select the transaction you want to exclude.
Once done, you can start adding those transactions or download the CSV files from your bank website. Let's ensure the date is correct before importing them. Open the file to edit the information.