Yes, an unused old-value Japan Post Letter Pack can still be used. As checked on November 3, 2026, the current values are ¥600 for Letter Pack Plus and ¥430 for Letter Pack Light. Japan Post says to attach stamps for the difference between the value printed on your envelope and the current value. For a ¥520 Plus envelope, that is ¥80; for a ¥370 Light envelope, ¥60. Put the additional stamps below the printed postage mark at the upper left. Japan Post’s old-value envelope FAQ, English Letter Pack guide.

This guide is official-source desk research, not a report of a counter or mailing test. The rates and rules may change, so check the linked Japan Post pages again when you actually send the item.

Illustration of checking an old prepaid envelope before mailing.
AI-generated conceptual illustration, not an actual product or scale drawing.

Read the printed value before buying stamps

Find Plus or Light on the envelope, then read its printed value. Use this calculation: current value for the same type minus the printed value. Do not compare a Plus envelope to the Light rate merely because the contents would fit in Light.

Envelope in your drawer Current value of that type Additional stamps
Unused Letter Pack Plus marked ¥520 ¥600 ¥80
Unused Letter Pack Light marked ¥370 ¥430 ¥60

These are checked examples, not a list of every old printed value. If yours has a different amount, read it and calculate the difference against its own type’s current value. An envelope already marked ¥600 Plus or ¥430 Light needs no top-up under the current rate. Japan Post’s general FAQ covers old-value envelopes by the difference, while the English guide explicitly gives the ¥520 and ¥370 examples. Japan Post: old-value FAQ, Letter Pack guide.

Where can the extra stamps go?

Japan Post directs you to place the difference in stamps below the postage mark at the upper left. The envelope also warns against writing or attaching anything above a line reserved for cancellation. The FAQ specifically permits the extra stamps in the stated position. If you cannot identify that area on a damaged or unusual envelope, show it to a postal counter rather than covering the postage mark or address. Japan Post: stamp placement.

Before posting, peel off and keep the customer copy of the tracking label; the number on it is how you can check tracking. This step applies to current and old Letter Packs alike. Japan Post: tracking sticker.

Illustration of keeping a tracking slip while checking an envelope.
AI-generated conceptual illustration, not an actual product or scale drawing.

Check that the envelope is still usable

Adding enough stamps does not make a used envelope reusable. Japan Post says a Letter Pack already delivered or returned cannot be used again, even with more stamps. It also lists damaged or modified envelopes and a damaged postage mark among acceptance problems. For Plus, a missing delivery-certificate portion is another reason it cannot be posted as it is. Japan Post: use and damaged envelope rules.

The contents still need to meet the service’s conditions. Letter Packs are domestic only, A4-sized and up to 4 kg; Light has a 3 cm thickness condition, while Plus is delivered face to face. A top-up pays the rate difference; it does not change Light into Plus or turn the envelope into an international service. Japan Post: Letter Pack types and conditions.

Hypothetical decision: You have an unused ¥370 Light envelope and a document that fits Light. Add ¥60 in stamps at the specified place, keep the tracking sticker, and use that envelope. If the finished item exceeds Light’s size or thickness condition, the ¥60 does not fix the service mismatch; choose a suitable service or ask the counter before sealing it. If the envelope has already been used, choose a new one.