Under CRA rules pension lump sums in box 18 on a T4A are eligible to be split with my spouse. Why does turbo tax not include the amount in the income splitting tool?

Yes, you can split the amount in Box 18 provided it is a lump-sum payment from an SPP or money purchase RPP.

Have you made sure to indicate on the T4A screen that Box 18 is a payment from an SPP or money purchase RPP?

I had completed the inputs as you indicated however the amount is not included when I split my pension income later on in the process. I noticed that the amounts show up as "other income" on line 13000. Could this be the problem?

We would recommend contacting our phone support team at 1-888-829-8608 as they will be better able to assist you. They can look at the return with you to see what is going on.