[Lesd]

 I planted International kidney  potatoes mid March , some in the ground and some in potato bags.
When I emptied one of the bags there were no potatoes, just top, the same result with those planted  in the ground. Any advjce/ comments pls.

[Yorkie]

Welcome to the forums 

Have you been adding any fertiliser to the potatoes? If so, what was it?

And how much watering have you been doing?

[Blewit]

International Kidney are marketed as a first early but for me they've always behaved like late seconds. I'd be inclined to give them another four weeks and check again or wait until the foliage starts to die back.