Kent Online Parish Clerks
The Answer - Settlement Certificate
You need to understand the mechanism of settlement in order to receive an answer to your question. My reply here is going to be bare bones and simplistic as the entire settlement criteria is complex and changed over time from the early 1600s through the 1800s.
All individuals were entitled to legal settlement (remember, women gained settlement by virtue of their husband's settlement or from her parent's settlement or from qualifying employment) with a particular parish. That settlement came, first, by virtue of birth in a parish in which the father had settlement. Settlement also came by virtue of serving apprenticeships and servitude for certain periods of time in a parish that was not the native parish of the person. There were additional mechanisms for legal settlement but I shall not go into those, here.
When a person who had legal settlement in a parish wished to take up residence in a different parish, he/she was given a Settlement Certificate by the parish overseers. The certificate, naturally, had the name of the parish of settlement and was addressed to the new receiving parish. The certificate served as a guarantee to the new parish that, should the person fall on hard times and become a burden on the parish relief, he or she could be sent back to the parish of settlement with no arguments. (Frequently, there were arguments and those can be found in Quarter Sessions records.)
Physically, in theory the Settlement document travelled with a person from place to place. If they were "removed" by the new parish, a Removal Order had to be issued and attached to the Settlement Certificate. The documents were literally pinned to the clothes of the person and he/she was sent packing, at the charge of the removing parish, by cart, back to the settled parish.
So, to find a Settlement Certificate one must look to the parish chest documents in the parish when the person was then residing, or sent back to.
The Settlement Certificate will contain a brief precis of the determination of settlement e.g. if the father was legally entitled to settlement in that parish then by what event, if the travelling person had last served employment that qualified him/her for legal settlement, and so on. In each instance supporting statements are provided to demonstrate the validity of the settlement and so you can quite often find birth dates, christening dates, parent's names, or details concerning qualifying employment.
If no Settlement Certificate can be found in the parish of residence it may be that, indeed, sloppy or careless maintenance of the parish chest material had resulted in the loss or destruction of the document. All is not lost though. A read through of the overseers accounts for the ejecting parish at the time the person was removed will reveal a payment made to the cart driver for taking the person to the parish limits and handing him/her over to the overseers of the settled parish. A similar payment was sometimes made by the settled parish to the ejecting parish to pay for the entire trip back to the settled parish.
If no Settlement Certificate can be found it may be that the person moved into the new parish without one or that it had been lost or destroyed before the period when he or she needed to be returned to their original parish of settlement. In either case, the parish overseers examined the individual. The examination proceeded much as a cross-examination in court does today. The Overseers asked the person a series of questions all designed to assist the Overseers in determining the rightful parish of settlement. The sometimes long interrogatories can contain almost complete genealogies of three generations of a person's ancestry. Sadly, though the vast majority were built on the strength of last qualifying employment. For that purpose, it was often necessary to ask the individual where he/she had lived and worked for quite a number of years before the Overseers could determine a proper place of settlement. It would be worth following up any leads to other parishes of residences mentioned in these examinations. These interrogatories are known as Settlement Examinations. Again, look to the parish chest material to locate these documents.
If no settlement certificate or removal order can be found for an ancestor despite several moves of residence through different parishes, you might want to start thinking in the terms that your ancestor had some form of dependable income in each parish. Very seldom were settlement certificates issued to or requested of people who had means to support themselves e.g. yeomen, gents, esquires, husbandmen, and so forth.