To compute the Net Debt / EBITDA ratio for HERA S.P.A. for 2022 using S&P’s methodology we proceed as follows:

**1. Net Debt**  
- Total financial liabilities (current + non‑current) = 5 689.9 M + 650.1 M = 6 340.0 M EUR  
- Add lease liabilities (current + non‑current) = 55.1 M + 21.3 M = 76.4 M EUR  
- Total debt = 6 340.0 M + 76.4 M = 6 416.4 M EUR  
- Cash and cash equivalents at end‑2022 = 1 942.4 M EUR  
- Net Debt = 6 416.4 M − 1 942.4 M = **4 474.0 M EUR**

**2. Adjusted EBITDA**  
- Operating profit (EBIT) = 533.8 M EUR  
- Add back depreciation & amortisation (non‑cash) = 478.6 M EUR  
- Add net provisions (allocation − release) = 188.5 M − 27.8 M = 160.7 M EUR  
- Subtract non‑cash capital gains = 41.6 M EUR  
- Add back share of profit of associates (non‑cash) = 10.0 M EUR  
- Adjusted EBITDA = 533.8 + 478.6 + 160.7 − 41.6 + 10.0 = **1 141.5 M EUR**

**3. Ratio**  
- Net Debt / EBITDA = 4 474.0 M / 1 141.5 M ≈ **3.9**

Thus, the estimated Net Debt / EBITDA ratio for 2022 is approximately 3.9.

<answer>3.9</answer>