The taxes settings page, has two fields:
The Tax ID: this is your business' tax ID number - it depends on your business country of registration, this will be set in invoices and for tax filing purposes.
Agreeing to automatic collection of Taxes by Pocketsflow: If you agree by selecting 'Yes' – this will make Pocketsflow your Merchant of Record and will collect and remit taxes on your behalf. This will increase the fees collected by Pocketsflow from 3% to 4%.