You are probably not being charged for Medicare Part D IRMAA, but rather only Medicare Part B IRMAA.

Income-Related Monthly Adjustments Amounts (IRMAA) are additional amounts of money charged to Medicare beneficiaries who have annual income (modified adjusted gross income (MAGI)) over certain limits.

The IRMAA charges are then paid in addition to both Medicare Part B and Medicare Part D premiums.

(You can see the annual changes in IRMAA limits in our Q1Medicare News section: https://Q1News.com/C/16.html)

However, Part D IRMAA will not be charged if you are not enrolled in a Medicare Part D plan - but, you will still need to pay your Medicare Part B IRMAA. 

As noted by the Centers for Medicare and Medicaid Services (CMS):
"If an individual does not have or no longer has Medicare prescription drug coverage, they shouldn’t be charged the Part D-IRMAA."  However, the CMS memo does continue on to note that "if someone didn’t pay the Part D-IRMAA that was owed before disenrolling from their prescription drug coverage, they are responsible for the past due amount."

(Source: Part D-Income Related Monthly Adjustment Amount—Frequently Asked Questions & Answers, from Anthony Culotta, Director Medicare Enrollment & Appeals Group, December 10, 2010)
You are paying only Part B IRMAA.  Using this 2022 example, the Medicare Part B IRMAA is $68 for couples who earn between $182,000 and $228,000 annually or individuals who earn $91,000 to $114,000.

During the same year, the Medicare Part D IRMAA is $12.40 for the same income brackets (couples who earn between $182,000 and $228,000 annually or individuals who earn $91,000 to $114,000).

Since this person was assessed $68, and does not have a Medicare Part D prescription drug plan, they are only being charged for their Part B IRMAA.

You can click here to read more about 2022 IRMAA payments ("2022 IRMAA: Slight increase in Medicare Part D IRMAA payments for most along with changes in the IRMAA brackets due to annual inflation adjustments.")