Go to Settings > Billing. Scroll to Invoices. Each row shows the date, the period, the amount, and the status. Select View on a row to open that invoice on Stripe.
If there are more than a few invoices, select Show older invoices.
Shopify billing: If Shopify bills your Taxomate plan, the list is called Shopify charges and shows the last 20 charges from Shopify. Taxomate does not send a separate invoice.
Accounting firms: If your accountant manages the plan for this account, Billing says "Managed by your accountant". Ask your accountant for the invoices.