10. Specific items continued
2019
2018
2017
Year ended 31 March
£m
£m
£m
Revenue
Italian business investigation
–
–
22
Retrospective regulatory matters
31
23
(2)
31
23
20
Operating costs
EE acquisition warranty claims
–
225
–
Restructuring charges
386
241
–
EE integration costs
–
46
215
Property rationalisation costs
36
28
–
Pension equalisation costs
26
–
–
Retrospective regulatory matters
(4)
26
481
Italian business investigation
(55)
22
238
Out of period irrecoverable VAT
–
–
30
Profit (loss) on disposal of businesses
5
(1)
(16)
394
587
948
Operating loss
425
610
968
Net finance expense
Interest expense on retirement benefit obligation
139
218
209
Interest on out of period irrecoverable VAT
–
–
1
139
218
210
Net specific items charge before tax
564
828
1,178
Taxation
Tax credit on specific items above
(112)
(87)
(154)
Tax credit on re-measurement of deferred tax
–
–
(63)
(112)
(87)
(217)
Net specific items charge after tax
452
741
961
restructuring charges during the year we incurred charges of £ 386m -2017 / 18 : £ 241m 2016 / 17 : £ nil primarily relating to leaver costs .
these costs reflect projects within our group-wide cost transformation programme and include costs related to the remaining integration of ee and £ 23m costs to close the bt pension scheme and provide transition payments to affected employees .
ee integration costs ee integration costs incurred in prior years -2017 / 18 : £ 46m 2016 / 17 : £ 215m relate to ee related restructuring and leaver costs .
in 2016 / 17 this also included a £ 62m amortisation charge relating to the write-off of it assets as we integrated the ee and bt it infrastructure .
in the current year remaining ee integration activities have been combined into the wider restructuring programme .
retrospective regulatory matters we have recognised a net charge of £ 27m -2017 / 18 : £ 49m 2016 / 17 : £ 479m in relation to regulatory matters in the year .
this reflects the completion of the majority of compensation payments to other communications providers in relation to ofcom ’ s march 2017 findings of its investigation into our historical practices on deemed consent by openreach and new matters arising .
of this £ 31m is recognised in revenue offset by £ 4m in operating costs .
pension equalisation costs during the year we recognised a charge of £ 26m -2017 / 18 : £ nil 2016 / 17 : £ nil in relation to the high court requirement to equalise pension benefits between men and women due to guaranteed minimum pension -gmp .
property rationalisation costs we have recognised a charge of £ 36m -2017 / 18 : £ 28m 2016 / 17 : £ nil relating to the rationalisation of the group ’ s property portfolio and a reassessment of lease-end obligations .
italian business investigation during the year we have released £ -55m provisions relating to settlement of various matters in our italian business -2017 / 18 : a charge of £ 22m 2016 / 17 : a charge of £ 238m .
interest expense on retirement benefit obligation during the year we incurred £ 139m -2017 / 18 : £ 218m 2016 / 17 : 209m of interest costs in relation to our defined benefit pension obligations .
see note 20 for more details .
tax on specific items a tax credit of £ 112m -2017 / 18 : £ 87m 2016 / 17 : 154m was recognised in relation to specific items .
10 .
specific items continued ee acquisition warranty claims in the prior year we reached settlements with deutsche telekom and orange in respect of any warranty claims under the 2015 ee acquisition agreement arising from the issues previously announced regarding our operations in italy .
this represents a full and final settlement of these issues and resulted in a specific item charge of £ 225m .

Question: What was the pension equilisation cost related to?
Answer: high court requirement to equalise pension benefits between men and women due to guaranteed minimum pension (GMP).