If we're 50, invest $26K in a simple 401k in 2020. TurTax is telling the limit is $19.5K. Is simple 401k different than a regular 401K in the amount allowed to Deduct?

For a SIMPLE 401(k), the maximum contribution for 2020 is $13,500.

The catch-up amount applicable to a SIMPLE 401(k) in 2020 is $3,000 for participants aged 50 and older.

Please read this IRS document for more information.

Do both spouses work for the business that has the Simple IRA?  And is that business profit enough to cover the simple IRA contribution?