How do I tell TurboTax to NOT generate the QBI credit for a non-qualifying Schedule C. It is a consulting practice and clearly NOT eligible.

Is the income on the tax return over $315,000 (Married Filing Jointly) / $157,500 (Single)?

At the VERY end of the business section, it should have a question if the business is a SSTB ("Specified Service Trade or Business").

Just because it is an SSTB, that doesn't mean it can have QBI.

A5. A qualified trade or business is any trade or business, with two exceptions:

1. Specified service trade or business (SSTB), which includes a trade or business involving the performance of services in the fields of health, law, accounting, actuarial science, performing arts, consulting, athletics, financial services, investing and investment management, trading, dealing in certain assets or any trade or business where the principal asset is the reputation or skill of one or more of its employees. This exception only applies if a taxpayer’s taxable income exceeds $315,000 for a married couple filing a joint return, or $157,500 for all other taxpayers
    
2. Performing services as an employee