Since 2019 I'm going thru bad respond from Sars I've been submitting my document but now they are telling me I've been paying less tax on my Irp5 which is submitting by Government not me please help

Since 2019 I'm going thru bad respond from Sars I've been submitting my document but now they are telling me I've been paying less tax on my Irp5 which is submitting by Government not me please help. now Sars want to take R2000 frm my salary and I'm owing them R13800 which is not my faulty