What is the function and purpose of this document? How should it be translated? I don't think a direct translation would make any sense to American readers--they would probably think, "Why does this document exist?" (That's what I'm thinking right now, having never driven a car in Japan...)
説明： I am sort of guessing here, but what this is is:
a paper （書） that confirms receipt of 軽自動車届出済証 (proof of receipt) of a light vehicle. 軽自動車届出済み証 is a document used in transfering ownership of light cars and motorcycles.
I hope this explanation and the links will help you understand this term in the context of your translation.
The references show that this is used when returning the licence plate affixed to the vehicle back to the office of registration.
It appears to be a document which is required if you have officially de-registered the vehicle (called 廃車 but what this is technically is simply de-registering it as a motor vehicle, or taking it out of service. This can be permanent or temporary).
This is used when temporarily de-registering the vehicle and when you intend to re-register it (again use it as a motor vehicle).
During the time the vehicle is not registered, obviously it is not legal to drive, but you can use it in a parking lot as a storage locker, surface on which to dry your clothes, or whatever. :-)
If you wish to permanently de-register the vehicle, simply arrange to have it disposed after submitting 廃車届け。 in this case you probably need to give the vehicle disposer a 廃車届け確認書 or something similar.
If you wish to re-register the vehicle in the future, you have to submit proof that it has been de-registered, which appears to be what 軽自動車届出済証返納済確認書 is.
So, in summary, it looks like this is a document that confirms receipt of the delivery(somewhat redundant?) of the number plate of the light vehicle back to the motor vechicle department.
It is interesting to note that the web links I found referred to motorcycles rather than 軽自動車. I believe the procedure for both are the same, but it is more common for motorcycles to change hands more frequently.
I believe 軽自動車届出済証 is the same thing as a 車検証（自動車検査証明書） for a full size vehicle.
If you¥'re not aware, there are regular automobiles in Japan and there are 軽自動車 which are under 660cc displacement and have other restrictions on size and shape.
The above link clearly reveals that 軽自動車届出済証 is just the vehicle registration for a 軽自動車. Therefore, 軽自動車届出済証返納済確認書 is the return of that vehicle registration. Therefore, it is proof that the vehicle has been de-commissioned. （廃車）
OK. I'm crystal clear on the part about this mF being a receipt for the yԓ͏oϏ form and the license plate.
However, I'm a little confused as yet about the actual function of the yԓ͏oϏ form. If the yԓ͏oϏ is a document used in transferring ownership of light cars and motorcycles, could I call the yԓ͏oϏ a "Light Vehicle Ownership Transfer Notification"? Or not.
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軽自動車届出済証返納済確認書
Confirmation of return of certificate of delivery for light vehicle
説明： I am sort of guessing here, but what this is is:
a paper （書） that confirms receipt of 軽自動車届出済証 (proof of receipt) of a light vehicle. 軽自動車届出済み証 is a document used in transfering ownership of light cars and motorcycles.
I hope this explanation and the links will help you understand this term in the context of your translation.
The references show that this is used when returning the licence plate affixed to the vehicle back to the office of registration.
It appears to be a document which is required if you have officially de-registered the vehicle (called 廃車 but what this is technically is simply de-registering it as a motor vehicle, or taking it out of service. This can be permanent or temporary).
This is used when temporarily de-registering the vehicle and when you intend to re-register it (again use it as a motor vehicle).
During the time the vehicle is not registered, obviously it is not legal to drive, but you can use it in a parking lot as a storage locker, surface on which to dry your clothes, or whatever. :-)
If you wish to permanently de-register the vehicle, simply arrange to have it disposed after submitting 廃車届け。 in this case you probably need to give the vehicle disposer a 廃車届け確認書 or something similar.
If you wish to re-register the vehicle in the future, you have to submit proof that it has been de-registered, which appears to be what 軽自動車届出済証返納済確認書 is.
So, in summary, it looks like this is a document that confirms receipt of the delivery(somewhat redundant?) of the number plate of the light vehicle back to the motor vechicle department.
It is interesting to note that the web links I found referred to motorcycles rather than 軽自動車. I believe the procedure for both are the same, but it is more common for motorcycles to change hands more frequently.
I believe 軽自動車届出済証 is the same thing as a 車検証（自動車検査証明書） for a full size vehicle.
If you¥'re not aware, there are regular automobiles in Japan and there are 軽自動車 which are under 660cc displacement and have other restrictions on size and shape.
The above link clearly reveals that 軽自動車届出済証 is just the vehicle registration for a 軽自動車. Therefore, 軽自動車届出済証返納済確認書 is the return of that vehicle registration. Therefore, it is proof that the vehicle has been de-commissioned. （廃車）
The translation workplace 
