There is no upper limit per se.  The law says, it phases out by 6% of the AGI above the minimum.  So for one person, the complete phaseout is 6% of $100K = $6,000.  For two, 6% of $200K = $12,000.

In the 2026 Federal and California Tax Update, Spidell has a table on page 1-3, which is partially correct. The error is on the line for MFJ both spouses ag 65+ — instead of adding $200K to the minimum amount, they only add $150K.

• For single or HOH:  the deduction phases out completely at $175K.
• For MFJ one spouse age 65+ : the deduction phaseout is $250K.
• For MFJ both spouses ag 65+: the deduction phaseout is $350K.                            Why Lacere is calculation phaseout only 250K not 350K?