Valuation and qualifying accounts (Tables)

12 Months Ended

Dec. 31, 2019

SEC Schedule, 12-09, Valuation and Qualifying Accounts [Abstract]

Summary of valuation and qualifying accounts

											$ million
			2019				2018				2017
	Trade and other receivables		Fixed asset investments		Trade and other receivables		Fixed asset investments		Trade and other receivables		Fixed asset investments
At 1 January – IAS 39	416		235		335		314		392		335
Adjustment on adoption of IFRS 9	—		—		115		(85	)	—		—
At 1 January – IFRS 9	416		235		450		229		392		335
Charged to costs and expenses	206		28		30		10		68		47
Charged to other accountsa	(2	)	—		(12	)	(1	)	13		3
Deductions	(111	)	(14	)	(52	)	(3	)	(138	)	(71	)
At 31 December	509		249		416		235		335		314

^a Principally exchange adjustments.