I have seen to many people try to do taxes themselves and then we have to go back 3 years and amend the returns because the taxpayer either is exposing themselves to audit risk or missed out on a great deduction that would have resulted in a larger refund 

Do I need to amend prior returns, or can I take the catchup all in 2023?

This is because you can file a "superseded" return instead of an amended return on/before the extension due date which can make error correction a little easier if you get a surprise K-1 from an investment in August or something like that.

He found I missed a few large deductions, and he can file amended returns.That's a while back, and I used CPAs since.

Especially in Partnership land - the complexities of amending a partnership return are not cheap, and if you have 20 partners that now need to all amend their returns to get their 100% bonus depreciation later, that is a lot of compliance fees just for not wanting to extend.If you just file as is with the 80% rules, you can always amend later if/when it gets bumped to 100%, so that isn't a significant problem, just an extra step.What I would not recommend doing is filing as 80%, and then not bothering to fix it if it goes to 100%. 

I paid less than $800 last year and that included filling an amended 2015 return.  

Also you are able to amend prior years which could help if anything was missed. 

Better to hire someone then to pay for someone to amend possible mistakes or missed strategies later! 

I have even had situations where I had to amend my taxes because the tax person screwed up.

You have to amend your 2023 tax return.