The burial year is blank but the death year is there.
I cannot assume and make the death year the same as the birth year?
I want to but I think I can't
Correct, you can't make assumptions. I think you mean can't make the death year the same as the burial year. But, the person may not be buried in the same year they die. There are people I knew who died long ago, were cremated, and the ashes have not yet been buried. You also cannot calculate death years based on birth years.