I left a job I hated last December. Shortly before I left I went on strike with everyone else. I asked my manager at the time to email payroll to let them know and make sure it would be deducted from my final payslip. She did, and I have confirmation they've been notified.
Now, 4 bloody months later they've sent me an invoice for the strike day saying that I was paid and "as I can appreciate they want to recoup the money". I did this deliberately so I didn't get landed with a surprise bill long aftert I had forgotten the hell that was that job.