To my knowledge, civil service has a 'formula' of sorts to ensure parity between newcomers and current officers. This includes factors such as education level, years of relevant experience, NS etc.

Compared to private sector, civil service does not focus that much last drawn pay. The offer (monthly) may at times even be lower than your last drawn! So you have to do your own math, and see if that offer x 16 months (12 months normal pay, about 4 mths of extra comprising mid-year bonus, 13th month, year-end bonus and performance bonus) is better than your current annual. That's why in most HR convos with potential hires, they always ask these candidates to calculate with 16 months in mind - because if its a last drawn monthly to offered monthly, usually its a paycut or just about even.