Can I make additional contributions to my SIPP after starting drawdown?

Yes, you can make further pension contributions if you are under age 75.

After you've flexibly accessed your pension, from that point on you can only contribute up to £4,000 each year to all money purchase pensions, including your AJ Bell Youinvest SIPP. Additionally, it is not possible to make use of any unused contribution allowance from previous tax years to increase this amount.