QB Issue Resolution:

Here, in case you do not have access, is the rule https://www.irs.gov/businesses/small-businesses-self-employed/tangible-property-final-regulations

 

Per line item or otherwise quantity indicated such that individual pricing would easily be determined is what I see.¬† If, as you say, all of your documentation states you bought a single “kit” for $6000 you might have to treat this NOT as safe harbor. Even then, certain purchases do not qualify and if, for example, your store displays are attached to the walls or floor it is my understanding they would not be safe harbor. Consult with your tax CPA on all matters related to deductibility

Resolution for Issue 'Can 20 items purchased as a set qualify for de minimis tangible property treatment?' available: Yes (Solved).
Source: Intuit Community forum.

Can 20 items purchased as a set qualify for de minimis tangible property treatment?: this issue or error code is a known issue in Quickbooks Online (QBO) and/or Quickbooks. Support for this issue is available either by self-service or paid support options. Experts are available to resolve your Quickbooks issue to ensure minimal downtime and continue running your business. First try to resolve the issue yourself by looking for a resolution described below. If it is a complex issue or you are unable to solve the issue, you may contact us by clicking here or by using other support options.

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