Yes, you can claim financial costs, including business insurance, as allowable expenses when filing your taxes, @ClareS. However, it's important to note that QuickBooks Self-Employed (QBSE) classifies your transactions as allowable or disallowable based on the specific category you choose during entry, the information you've entered in your tax profile, and any bank rules that have been set.
To ensure your expenses are reported accurately, I recommend reviewing the categories assigned to your transactions. Each classification is associated with specific box numbers on the SA103F, which determine whether the expense qualifies as allowable on your Self Assessment tax return. For more information, please visit the HMRC website.
If you need further guidance in selecting the appropriate account for tracking these expenses, consider consulting your accountant.
To change the category, simply go to the Transactions page and locate the relevant expense. Click the category and recategorise it to the correct one.

You can also reach out to our Customer Care Team to perform a screen-sharing session to assist you with locating the incorrectly categorised expense transactions that caused them to appear in your disallowable expenses.
This thread remains open for any further questions regarding your transaction categories. Please don’t hesitate to Reply with any additional details.