Final answer:
True, because with 25 years of service and only 23 months post-October 1, 1991, 90% of the federal pension is indeed non-taxable in Oregon, as dictated by the cutoff date for employment.
Step-by-step explanation:
When discussing federal pensions and their taxability, each state may have different rules about how pension income is taxed. According to Oregon law, if you have worked for the US Post Office and became an employee before October 1, 1991, a portion of your federal pension may be exempt from Oregon state taxes. With 25 years of service, and only 23 months of that time after the cutoff date, the majority of your employment was before the cutoff, leading to 90% of your federal pension being non-taxable in Oregon. This is true because the pension is based on a formula that includes your number of months of service before and after the cutoff date, and most of the service was before the date in question.