As per your query you need to give the same UAN No. to your new employer and should clearly state that i am working in another organization also who is deducting my PF. An employee should not have two UAN No. since it is against the rules to have two UAN No.
If by mistake two UAN's have been allotted, you have to transfer your PF Balance and get the old one deactivated.
You should tell both your employers regarding your work in another organization.
Hope i am able to solve you query.
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Thanks & Best regards
CA Shubham Bansal