SAP Note 26619 - Tax and NI calculated on -ve Taxable, NIable pay

Symptom:

Tax and NI calculated even when the Taxable pay and NIable pay figures are negative.

Cause and prerequisites

The tax and NI routines should not even be called when this occurs

Solution
Ensure they are not called when negative gross values
In the case of tax the following rules have been incorporated.
If PAYE is calculated on a cumulative basis then tax should be
calculated and a refund made. In the test PAYE is on a week1/month1
basis and calculating positive deduction. Rules therefore are.
1) In a week1/month1 basis no tax deducted or refunded when taxable pay for the period is negative.
2) In cumulative basis if positive taxable pay year to date is reduced by a negative period taxable pay, and total for year is still positive, then PAYE fires and tax is refunded.
3) If a negative taxable pay is for the whole of tax year then fatal error and employee rejected.