I have just issued my first invoice, can QB forecast my UK corporation tax liability so I know how much I need to put into reserve?

Hello, @lee_osborne.

Currently, the ability to calculate and file corporation tax in QuickBooks Online is not available. While that feature isn’t currently in our development roadmap, you can use the previous years profit and loss in calculating your corporation taxes.

Meanwhile, you can enter a bill or an expense transaction to record a corporation tax. Also, you may create Other Expenses type account (i.e Corporate Expense Account) or a liability account where your corporation tax is posted to from the retained earnings. 

Lastly, I'd recommend consulting with an accountant so you'll be assisted accurately in calculating and filling your corporate taxes.

You can always leave your comments below if you have other questions. I'm just a few clicks away.