If your venue is tax-registered (VAT/GST), you have to provide your clients with a tax invoice instantly upon request. Although Tagvenue will be deducting its commission rate (15%) from the payout, the client should receive a tax receipt for the full amount that they have paid.
Here is an illustration of a UK venue to clarify why:
If you charge £100 for a venue booking, your sales come to £100. If you included 20% VAT in the pricing, the client can claim £20 of that amount as VAT if they are a VAT-registered company.
Tagvenue will charge you £15 (15% of £100). This fee is an independent transaction (sales cost) between you and Tagvenue and not related to the one between you and the client.
Despite that, technically speaking, these are two separate transactions, Tagvenue chooses to handle them as one to make the service easier by deducting the £15 from the £100 before paying you as a Venue manager rather than paying you £100 up front and then billing you individually for the additional £15.
Therefore, even though it may appear that you are responsible for the entire booking's VAT cost facing the client, you should keep in mind that the 15% Service Fee is a sales expense that you can deduct from your financial accounting.