Brian Reynolds

I receive a pension of $946.56 monthly from my former employer. Is a monthly payment considered a lump sum payment that is taxable at 20%? Or should it be taxed at the regular 10% taxable rate for that income level? For 13 years I was taxed at the 10% rate. My company was sold and the new company has stated the 20% tax rate is mandatory. Is that the case? Thank you, Brian Reynolds