The present value, without deducting any plan assets, of expected future payments required to settle the obligation resulting from employee service in the current and prior periods. [Refer: Plan assets, at fair value]

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 19
-IssueDate 2019-01-01
-Paragraph 57
-Subparagraph a
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=19&code=ifrs-tx-2019-en-r&anchor=para_57_a&doctype=Standard
-URIDate 2019-03-27

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The fair value of defined benefit plan assets. Plan assets comprise assets held by a long-term employee benefit fund and qualifying insurance policies. [Refer: At fair value [member]]

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Pensions and other post retirement benefits - Results of the most recent actuarial valuations (Details) - GBP (£) £ in Millions	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2016
Disclosure of defined benefit plans [line items]
Funding surplus/(deficit)	£ (953)	£ (218)	£ (263)
National Grid UK Pension Scheme - Section A
Disclosure of defined benefit plans [line items]
Fair value of plan assets		6,551
Actuarial value of benefits due to members		£ 6,502
Market value as percentage of benefits		101.00%
Funding surplus/(deficit)		£ 49
Funding surplus/(deficit) net of tax		41
National Grid UK Pension Scheme - Section B
Disclosure of defined benefit plans [line items]
Fair value of plan assets		5,765
Actuarial value of benefits due to members		£ 5,831
Market value as percentage of benefits		99.00%
Funding surplus/(deficit)		£ (66)
Funding surplus/(deficit) net of tax		(55)
NGEG of ESPS
Disclosure of defined benefit plans [line items]
Fair value of plan assets				£ 2,553
Actuarial value of benefits due to members				£ 3,053
Market value as percentage of benefits				84.00%
Funding surplus/(deficit)				£ (500)
Funding surplus/(deficit) net of tax				£ (415)
UK \| Pensions
Disclosure of defined benefit plans [line items]
Fair value of plan assets	14,364	15,507	15,330
Funding surplus/(deficit)	£ 1,520	£ 1,231	£ 1,104