Jean,
As you know your Medicare payment are based on the prior year tax returns.
If there are income changes to your Income you need to file an appeal . The way to do this is to submit Social Security Form SSA-44.
Click this link for the form https://www.ssa.gov/forms/ssa-44-ext.pdf
Form SSA-44 is a form provided by the Social Security Administration (SSA) that you can use to apply for a reduction in your IRMAA ( higher premium charged by Medicare Part B and Medicare Part D to individuals with higher incomes). If you’ve been notified that your premiums for either Medicare part B or prescription drug coverage include an IRMAA, then you can fill out and submit this form if you experience a life-changing event that reduces your income.
To submit your completed form SSa-44, you can either mail the form and your documentation to your local Social Security office or you can take it in person. The benefit of visiting an office in person is that you can show your documents to an SSA employee instead of mailing them to the office and being without them for any period of time.
Victor Santucci EA