Step 1: Identify the relevant industry
TenneT Holding B.V. is described as a "transmission system operator" providing an essential infrastructure service (electricity transmission) with revenue derived from "Energy Transmission Charges" and subject to comprehensive regulation. Therefore, it falls under the "Regulated Utilities" industry.

Step 2: Estimate Adjusted EBITDA
For Regulated Utilities, EBITDA is generally reported EBITDA unless distorted by pass-through costs. Given the large pass-through nature of congestion revenue (evidenced by the massive swing in working capital and revenue), we start with the reported operating loss and add back depreciation and amortization:
EBITDA = Profit Loss From Operating Activities + Depreciation And Amortisation Expense
EBITDA = -976,000,000 + 1,233,000,000 = 257,000,000 EUR
Under S&P adjustments, operating leases are reclassified as debt, and the rent expense is split into depreciation and imputed interest. Therefore, we must add back the lease rent expense to EBITDA and subtract the imputed interest later.
Lease rent expense is estimated as the total repayments of lease liabilities from the cash flow statement: 221,000,000 EUR.
Pension adjustments and other normalizations are typically 0 without specific disclosure requiring adjustment. Joint ventures are accounted for using the equity method, and proportional consolidation is not typically applied for regulated utilities unless specific criteria are met; we use the reported share of profit.
Adjusted_EBITDA = EBITDA + adjustment_leases
Adjusted_EBITDA = 257,000,000 + 221,000,000 = 478,000,000 EUR

Step 3: Estimate FFO
FFO = Adjusted_EBITDA - cash_interest - cash_taxes
To find cash_interest, we start with Finance Costs (300,000,000 EUR) and subtract the imputed lease interest (we estimate this by assuming a ~5% interest rate on the average lease liability, or use 50% as a standard proxy for the interest component of lease rent: ~110,500,000 EUR). Alternatively, S&P generally assumes a portion of the lease rent is interest. Let's use the standard proxy where roughly 50% of lease rent is interest (110.5M). 
Cash interest (excluding leases) = Finance Costs = 300,000,000 EUR.
Total Cash Interest = 300,000,000 (reported) + 110,500,000 (lease interest) = 410,500,000 EUR.
*(Note: Cash interest from financing activities is 202M, but S&P calculates interest on an accrual basis for FFO, adjusting for lease imputed interest).*
Cash taxes are given in the cash flow statement as Income Taxes Paid: 231,000,000 EUR. However, the reported income tax expense is -354,000,000 EUR. Since FFO typically uses cash taxes paid, we use 231,000,000 EUR.
FFO = 478,000,000 - 410,500,000 - 231,000,000 = -163,500,000 EUR

Step 4: Estimate Adjusted Debt
Reported Debt = Long-term Borrowings + Short-term Borrowings + Current Bank Overdrafts
Reported Debt = 19,006,000,000 + 1,339,000,000 + 64,000,000 = 20,409,000,000 EUR
Leases = Noncurrent Lease Liabilities + Current Lease Liabilities = 235,000,000 + 169,000,000 = 404,000,000 EUR
Hybrid Capital: S&P typically treats 50% of hybrid capital as debt if it has intermediate equity content. 50% of 2,125,000,000 = 1,062,500,000 EUR.
Pension deficit: Net Defined Benefit Liability = Noncurrent Recognised Liabilities Defined Benefit Plan - Deferred Tax Assets (if related, but here DTA is largely from accelerated depreciation). We use the Defined Benefit Liability = 351,000,000 EUR.
Other debt-like items: None specifically identified.
Elible cash = Cash And Cash Equivalents = 3,204,000,000 EUR.
Adjusted_Debt = Reported_Debt + Leases + Hybrid_debt_portion + Pension_deficit - Eligible_cash
Adjusted_Debt = 20,409,000,000 + 404,000,000 + 1,062,500,000 + 351,000,000 - 3,204,000,000 = 19,022,500,000 EUR

Step 5: Calculate FFO / Adjusted Debt
FFO / Adjusted_Debt = -163,500,000 / 19,022,500,000 = -0.008593...

Rounding to four decimal places gives -0.0086.

<answer>-0.0086</answer>