Is report of actuary is compulsory for valuation of gratuity as per ind as-19

International accounting standards IAS 19, ASC 715, FRS 17:
Actuarial valuations are also mandated by other accounting standards, such as IFRS (IAS 19) or US GAAP (ASC 715). Indian companies which are subsidiaries of companies registered outside India, will often require actuarial valuations and reporting to be done under either of these international accounting standards. This is required for consolidating their results into that of their parent companies. The requirement to conduct actuarial valuation under these accounting standards is incremental to the requirements of AS 15 or Ind AS 19.

So, Ind AS: 19 not mandate Actuary Valuation, it mandate if inclusion of foreign units, H.O, Branch etc.

Yes, It is mandatory to get an Actuarial Report in compliance of IndAS 19 due to Regulatory Requirement under Section 129 (ie Financial Report is to be prepared) and 133 (i.e Financial Reporting to be complied with relavant Accounting Standards such as AS 15 (Revised 2005) and IndAS 19 ) of the Companies Act 2013, furthermore Break-up of Employee Benefit Liabilitiies and Assets  is to shown under the heading of Current and Non Current Liabilities/Assets for compliance of Schedule III to Compnies Act, 2013.

I agree with your thinking 

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Strictly, Ind AS 19 "encourages" but does not mandate a qualified actuary (para 59). In practice, it is effectively necessary:

• Ind AS 19 requires the Projected Unit Credit method with assumptions on discount rate (government bond yields), salary escalation, attrition and mortality. Auditors (SA 620, using the work of an expert) and regulators expect an actuarial report for anything beyond immaterial amounts.

• AS 15 (non-Ind AS): small and medium companies (SMCs) and small non-corporate entities may use other rational methods, e.g. accrued-benefit calculation, without actuarial valuation (AS 15 SME exemptions).

• Tax: provision for gratuity is deductible only if contributed to an approved gratuity fund (Sec 36(1)(v), 40A(7)). Unfunded provisions are disallowed until paid (Sec 43B(b)).

• If the company funds through an LIC group gratuity scheme, LIC's actuarial statement is commonly used. Ensure the assumptions match Ind AS 19 (discount rate as at the reporting date).

Yes, It is mandatory.