Difference between source code 4001 and 4002?

The retirement form questions on TaxTim ask if I have code 4002 on my IRP5. I don't have 4002 (ARREAR PENSION FUND CONTRIBUTIONS), but I have 4001 (CURRENT PENSION FUND CONTRIBUTIONS).

Can I not claim for this contribution?

No, unfortunately these are two different deductions. If you see 4001 on your IRP5 then this will be taken into account on the IRP5 section. You will still receive the benefit.