You sure can!
Head to the Account tab and click ‘One-off contributions’ – this is where you can top-up your Lifetime ISA anytime with a one-off sum. We’ll stop you going over your Lifetime ISA’s £4,000 allowance, so don’t worry about accidentally topping it up too much.
Once you have paid via this method, the money will show as pending in your account, and when it has reached us from your bank, you’ll see it added to your balance (and your time to buy will go down, too).