Why is my ticket number reading Invalid

Response to this request is long overdue. By law, under all circumstances, Uganda Police Force should have responded by now (details). You can complain by requesting an internal review.

Dear Uganda Police Force,

Iam trying to input my ticket number(MNA3969538) for payment into the URA web but it keeps saying its invalid, Nkoze ntya i want to get my self cleared.

Yours faithfully,

Katongole Akram