Income taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2020	Mar. 31, 2019
Deferred tax liabilities
Capital allowances for tax purposes				$ 4,141	$ 5,504
Intangible assets				2,778	3,183
Prepaid expenses				164	208
Deferred foreign currency gains				8,402	5,861
Investment in subsidiaries				157	151
Deferred commissions				894	952
Lease assets				842	483
Other				79	146
Gross deferred tax liabilities				17,457	16,488
Set-off of deferred tax balances				(6,021)	(7,314)
Net deferred tax liabilities				11,436	9,174
Deferred tax assets
Deferred revenue				1,059	1,161
Capital allowances for tax purposes				1,137	1,686
Accruals				2,986	3,334
Tax losses				2,578	3,985
Stock based compensation				396	233
Deferred foreign currency losses				374	279
Recurring commission liability				169	74
Lease liabilities				913	524
Other				265	245
Gross deferred tax assets				9,877	11,521
Set-off of deferred tax balances				(6,021)	(7,314)
Net deferred tax assets before valuation allowance				3,856	4,207
Less valuation allowance				(748)	(1,010)
Net deferred tax assets				3,108	3,197
Net deferred tax liability	$ (5,977)	$ (5,977)	$ (3,238)	$ (8,328)	$ (5,977)
The gross movement in net deferred tax assets/(liabilities) is as follows:
Opening balance	(5,977)	(3,238)
Adjustment on initial application of ASC 326, 606, 842	39	(730)
Foreign currency translation	2,240	993
Credited to equity (other comprehensive income)	(40)	84
Statement of Income charge	(4,590)	(3,086)	1,766
Ending balance	$ (8,328)	$ (5,977)	$ (3,238)