What is an A1 certificate and why does it matter for workers sent to Norway?

An A1 certificate proves which country collects social security contributions for a cross-border worker. For EU/EEA workers posted to Norway, an A1 from the home country means the employer pays social security there (not Norwegian trygdeavgift/arbeidsgiveravgift on those items), saving roughly 14.1% employer contributions plus 7.6% employee contributions. The certificate must be applied for in the home country BEFORE deployment — retroactive applications are possible but unreliable. Without an A1, Norwegian social security applies by default. For PAYE workers with an A1, the withholding rate drops from 25% to 17.4%. Maximum posting period: 24 months (extendable in special cases).