Must IRS approval be sought before a plan is entitled to "tax qualified" benefits?

No. Although not required, an employer may apply for an advance determination as to the tax qualified status of its retirement plan as to form and the application of the non-discrimination tests. The written advance determination is commonly referred to as a determination letter which, when issued, indicates that in the opinion of the Internal Revenue Service, the terms of the plan or the application of the non-discrimination tests are acceptable. The determination letter does not "guarantee" that the operation of the plan will conform to applicable law in that conditions may develop that may jeopardize the continued qualification of the plan, e.g., it may fail to satisfy the non-discrimination requirements or the distribution requirements. The Internal Revenue Service charges a fee, which depends on the type of request applied for.