How to deal with an "Election by a Principal and the Principal’s Agent" tax remittance in our bookkeeping

We are registered to collect and remit sales tax in Quebec. 

We've started selling online through a platform (Depop) that collects and remits sales tax on behalf of their sellers. They require the Election by a Principal and Principal's Agent form to show they are remitting taxes on behalf of registered businesses, which seems pretty straightforward. My question is, how do I deal with this in my bookkeeping?

We receive the full payment from the customer (Sale + shipping + sales tax) into our Paypal account, then the commission + the sales tax are immediately paid out to Depop (the selling platform) from the Paypal account.

For example: 

Buyer paid $75 + $13 Shipping + 11.44 in HST ON - we receive a deposit of $99.44 in our Paypal account.

Depop immediately receives a payment of $8.80 (commission) + the 11.44 sales tax

Normally I would just create an expense with the $8.80 commission -- but now where does the $11.44 HST go? Is it considered an expense as well if we have elected to have Depop remit our sales tax?

Thanks community!