Have sale contract for October 2019. Buyer paid 75% in 2019 and 25% in 2020. What yr to file?

Contract for a 2nd house sale states that payments by buyer must complete by October 2019.   Buyer was late on payment.  Buyer paid 75% of the house price in 2019, and 25% in early 2020.

Do I have to file 75% income/capital-gains in 2019, and 25% income/capital-gains in 2020 and ignore the contract pay by dates?