1099B

I moved my shares from one brokerage to another about 2 years ago.  I sold shares in 2020 but since i did not start the account with Fidelity they did not report a cost basis.  Do i have to use FIFO or LIFO to identify the shares i sold?

 

Can i not just go thru my records and identify the shares that i sold myself rather than have large gains if i had to use FIFO since some of the stock is over 20 years old and has significant gains.  If i use LIFO i will have to pay short term gains (income) on a good amount of the stock proceeds.  Can i just identify the stock that i sold that is more than a year old?  Sort of LIFO minus a year.  That will give me the least gains this year and reduce the tax burden this year.