The Wealth of Nations by Part 1 Chapter 10 Page 124

Though a certificate carries along with it no testimonial of good behaviour, and certifies nothing but that the person belongs to the parish to which he really does belong, it is altogether discretionary in the parish officers either to grant or to refuse it. A mandamus was once moved for, says Doctor Burn, to compel the churchwardens and overseers to sign a certificate; but the court of King’s Bench rejected the motion as a very strange attempt.

The very unequal price of labour which we frequently find in England in places at no great distance from one another is probably owing to the obstruction which the law of settlements gives to a poor man who would carry his industry from one parish to another without a certificate. A single man, indeed, who is healthy and industrious, may sometimes reside by sufferance