A PO BOX number can be less than or more than four digit. For post office boxes, the general rule is that each box has its own ZIP+4 code.
The last four digit is often one of the following:
1. Zero plus the last three digits of the box number (eg. PO BOX 1001, Los Angeles CA 90001-0001).
2. The last four digits of the box number (eg. PO BOX 9991, Twin Peaks CA 92391-9991).
3. If the box number is less than four digits, enough zeros prepended to the front of the box number to produce a four-digit number(eg. PO BOX 1, Shreveport LA 71161-0001).
However, there is no uniform rule, the zip code plus four is for reference only, the ZIP+4 code must be looked up individually for each box in the USPS offical website.
PO BOX 399275, SAN FRANCISCO, CA 94139-9275
PO BOX 399276, SAN FRANCISCO, CA 94139-9276
PO BOX 399277, SAN FRANCISCO, CA 94139-9277
PO BOX 399278, SAN FRANCISCO, CA 94139-9278
PO BOX 399279, SAN FRANCISCO, CA 94139-9279
PO BOX 399280, SAN FRANCISCO, CA 94139-9280
PO BOX 399281, SAN FRANCISCO, CA 94139-9281
PO BOX 399282, SAN FRANCISCO, CA 94139-9282
PO BOX 399283, SAN FRANCISCO, CA 94139-9283
PO BOX 399284, SAN FRANCISCO, CA 94139-9284
PO BOX 399285, SAN FRANCISCO, CA 94139-9285
PO BOX 399286, SAN FRANCISCO, CA 94139-9286
PO BOX 399287, SAN FRANCISCO, CA 94139-9287
PO BOX 399288, SAN FRANCISCO, CA 94139-9288
PO BOX 399289, SAN FRANCISCO, CA 94139-9289
PO BOX 399290, SAN FRANCISCO, CA 94139-9290
PO BOX 399291, SAN FRANCISCO, CA 94139-9291
PO BOX 399292, SAN FRANCISCO, CA 94139-9292
PO BOX 399293, SAN FRANCISCO, CA 94139-9293
PO BOX 399294, SAN FRANCISCO, CA 94139-9294
PO BOX 399295, SAN FRANCISCO, CA 94139-9295
PO BOX 399296, SAN FRANCISCO, CA 94139-9296
PO BOX 399297, SAN FRANCISCO, CA 94139-9297
PO BOX 399298, SAN FRANCISCO, CA 94139-9298
PO BOX 399299, SAN FRANCISCO, CA 94139-9299
PO BOX 399300, SAN FRANCISCO, CA 94139-9300
PO BOX 399301, SAN FRANCISCO, CA 94139-9301
PO BOX 399302, SAN FRANCISCO, CA 94139-9302
PO BOX 399303, SAN FRANCISCO, CA 94139-9303
PO BOX 399304, SAN FRANCISCO, CA 94139-9304
PO BOX 399305, SAN FRANCISCO, CA 94139-9305
PO BOX 399306, SAN FRANCISCO, CA 94139-9306
PO BOX 399307, SAN FRANCISCO, CA 94139-9307
PO BOX 399308, SAN FRANCISCO, CA 94139-9308
PO BOX 399309, SAN FRANCISCO, CA 94139-9309
PO BOX 399310, SAN FRANCISCO, CA 94139-9310
PO BOX 399311, SAN FRANCISCO, CA 94139-9311
PO BOX 399312, SAN FRANCISCO, CA 94139-9312
PO BOX 399313, SAN FRANCISCO, CA 94139-9313
PO BOX 399314, SAN FRANCISCO, CA 94139-9314
PO BOX 399315, SAN FRANCISCO, CA 94139-9315
PO BOX 399316, SAN FRANCISCO, CA 94139-9316
PO BOX 399317, SAN FRANCISCO, CA 94139-9317
PO BOX 399318, SAN FRANCISCO, CA 94139-9318
PO BOX 399319, SAN FRANCISCO, CA 94139-9319
PO BOX 399320, SAN FRANCISCO, CA 94139-9320
PO BOX 399321, SAN FRANCISCO, CA 94139-9321
PO BOX 399322, SAN FRANCISCO, CA 94139-9322
PO BOX 399323, SAN FRANCISCO, CA 94139-9323
PO BOX 399324, SAN FRANCISCO, CA 94139-9324
PO BOX 399325, SAN FRANCISCO, CA 94139-9325
PO BOX 399326, SAN FRANCISCO, CA 94139-9326
PO BOX 399327, SAN FRANCISCO, CA 94139-9327
PO BOX 399328, SAN FRANCISCO, CA 94139-9328
PO BOX 399329, SAN FRANCISCO, CA 94139-9329
PO BOX 399330, SAN FRANCISCO, CA 94139-9330
PO BOX 399331, SAN FRANCISCO, CA 94139-9331
PO BOX 399332, SAN FRANCISCO, CA 94139-9332
PO BOX 399333, SAN FRANCISCO, CA 94139-9333
PO BOX 399334, SAN FRANCISCO, CA 94139-9334
PO BOX 399335, SAN FRANCISCO, CA 94139-9335
PO BOX 399336, SAN FRANCISCO, CA 94139-9336
PO BOX 399337, SAN FRANCISCO, CA 94139-9337
PO BOX 399338, SAN FRANCISCO, CA 94139-9338
PO BOX 399339, SAN FRANCISCO, CA 94139-9339
PO BOX 399340, SAN FRANCISCO, CA 94139-9340
PO BOX 399341, SAN FRANCISCO, CA 94139-9341
PO BOX 399342, SAN FRANCISCO, CA 94139-9342
PO BOX 399343, SAN FRANCISCO, CA 94139-9343
PO BOX 399344, SAN FRANCISCO, CA 94139-9344
PO BOX 399345, SAN FRANCISCO, CA 94139-9345
PO BOX 399346, SAN FRANCISCO, CA 94139-9346
PO BOX 399347, SAN FRANCISCO, CA 94139-9347
PO BOX 399348, SAN FRANCISCO, CA 94139-9348
PO BOX 399349, SAN FRANCISCO, CA 94139-9349
PO BOX 399350, SAN FRANCISCO, CA 94139-9350
PO BOX 399351, SAN FRANCISCO, CA 94139-9351
PO BOX 399352, SAN FRANCISCO, CA 94139-9352
PO BOX 399353, SAN FRANCISCO, CA 94139-9353
PO BOX 399354, SAN FRANCISCO, CA 94139-9354
PO BOX 399355, SAN FRANCISCO, CA 94139-9355
PO BOX 399356, SAN FRANCISCO, CA 94139-9356
PO BOX 399357, SAN FRANCISCO, CA 94139-9357
PO BOX 399358, SAN FRANCISCO, CA 94139-9358
PO BOX 399359, SAN FRANCISCO, CA 94139-9359
PO BOX 399360, SAN FRANCISCO, CA 94139-9360
PO BOX 399361, SAN FRANCISCO, CA 94139-9361
PO BOX 399362, SAN FRANCISCO, CA 94139-9362
PO BOX 399363, SAN FRANCISCO, CA 94139-9363
PO BOX 399364, SAN FRANCISCO, CA 94139-9364
PO BOX 399365, SAN FRANCISCO, CA 94139-9365
PO BOX 399366, SAN FRANCISCO, CA 94139-9366
PO BOX 399367, SAN FRANCISCO, CA 94139-9367
PO BOX 399368, SAN FRANCISCO, CA 94139-9368
PO BOX 399369, SAN FRANCISCO, CA 94139-9369
PO BOX 399370, SAN FRANCISCO, CA 94139-9370
PO BOX 399371, SAN FRANCISCO, CA 94139-9371
PO BOX 399372, SAN FRANCISCO, CA 94139-9372
PO BOX 399373, SAN FRANCISCO, CA 94139-9373
PO BOX 399374, SAN FRANCISCO, CA 94139-9374
PO BOX 399375, SAN FRANCISCO, CA 94139-9375
PO BOX 399376, SAN FRANCISCO, CA 94139-9376
PO BOX 399377, SAN FRANCISCO, CA 94139-9377
PO BOX 399378, SAN FRANCISCO, CA 94139-9378
PO BOX 399379, SAN FRANCISCO, CA 94139-9379
PO BOX 399380, SAN FRANCISCO, CA 94139-9380
PO BOX 399381, SAN FRANCISCO, CA 94139-9381
PO BOX 399382, SAN FRANCISCO, CA 94139-9382
PO BOX 399383, SAN FRANCISCO, CA 94139-9383
PO BOX 399384, SAN FRANCISCO, CA 94139-9384
PO BOX 399385, SAN FRANCISCO, CA 94139-9385
PO BOX 399386, SAN FRANCISCO, CA 94139-9386
PO BOX 399387, SAN FRANCISCO, CA 94139-9387
PO BOX 399388, SAN FRANCISCO, CA 94139-9388
PO BOX 399389, SAN FRANCISCO, CA 94139-9389
PO BOX 399390, SAN FRANCISCO, CA 94139-9390
PO BOX 399391, SAN FRANCISCO, CA 94139-9391
PO BOX 399392, SAN FRANCISCO, CA 94139-9392
PO BOX 399393, SAN FRANCISCO, CA 94139-9393
PO BOX 399394, SAN FRANCISCO, CA 94139-9394
PO BOX 399395, SAN FRANCISCO, CA 94139-9395
PO BOX 399396, SAN FRANCISCO, CA 94139-9396
PO BOX 399397, SAN FRANCISCO, CA 94139-9397
PO BOX 399398, SAN FRANCISCO, CA 94139-9398
PO BOX 399399, SAN FRANCISCO, CA 94139-9399
PO BOX 399400, SAN FRANCISCO, CA 94139-9400
PO BOX 399401, SAN FRANCISCO, CA 94139-9401
PO BOX 399402, SAN FRANCISCO, CA 94139-9402
PO BOX 399403, SAN FRANCISCO, CA 94139-9403
PO BOX 399404, SAN FRANCISCO, CA 94139-9404
PO BOX 399405, SAN FRANCISCO, CA 94139-9405
PO BOX 399406, SAN FRANCISCO, CA 94139-9406
PO BOX 399407, SAN FRANCISCO, CA 94139-9407
PO BOX 399408, SAN FRANCISCO, CA 94139-9408
PO BOX 399409, SAN FRANCISCO, CA 94139-9409
PO BOX 399410, SAN FRANCISCO, CA 94139-9410
PO BOX 399411, SAN FRANCISCO, CA 94139-9411
PO BOX 399412, SAN FRANCISCO, CA 94139-9412
PO BOX 399413, SAN FRANCISCO, CA 94139-9413
PO BOX 399414, SAN FRANCISCO, CA 94139-9414
PO BOX 399415, SAN FRANCISCO, CA 94139-9415
PO BOX 399416, SAN FRANCISCO, CA 94139-9416
PO BOX 399417, SAN FRANCISCO, CA 94139-9417
PO BOX 399418, SAN FRANCISCO, CA 94139-9418
PO BOX 399419, SAN FRANCISCO, CA 94139-9419
PO BOX 399420, SAN FRANCISCO, CA 94139-9420
PO BOX 399421, SAN FRANCISCO, CA 94139-9421
PO BOX 399422, SAN FRANCISCO, CA 94139-9422
PO BOX 399423, SAN FRANCISCO, CA 94139-9423
PO BOX 399424, SAN FRANCISCO, CA 94139-9424
PO BOX 399425, SAN FRANCISCO, CA 94139-9425
PO BOX 399426, SAN FRANCISCO, CA 94139-9426
PO BOX 399427, SAN FRANCISCO, CA 94139-9427
PO BOX 399428, SAN FRANCISCO, CA 94139-9428
PO BOX 399429, SAN FRANCISCO, CA 94139-9429
PO BOX 399430, SAN FRANCISCO, CA 94139-9430
PO BOX 399431, SAN FRANCISCO, CA 94139-9431
PO BOX 399432, SAN FRANCISCO, CA 94139-9432
PO BOX 399433, SAN FRANCISCO, CA 94139-9433
PO BOX 399434, SAN FRANCISCO, CA 94139-9434
PO BOX 399435, SAN FRANCISCO, CA 94139-9435
PO BOX 399436, SAN FRANCISCO, CA 94139-9436
PO BOX 399437, SAN FRANCISCO, CA 94139-9437
PO BOX 399438, SAN FRANCISCO, CA 94139-9438
PO BOX 399439, SAN FRANCISCO, CA 94139-9439
PO BOX 399440, SAN FRANCISCO, CA 94139-9440
PO BOX 399441, SAN FRANCISCO, CA 94139-9441
PO BOX 399442, SAN FRANCISCO, CA 94139-9442
PO BOX 399443, SAN FRANCISCO, CA 94139-9443
PO BOX 399444, SAN FRANCISCO, CA 94139-9444
PO BOX 399445, SAN FRANCISCO, CA 94139-9445
PO BOX 399446, SAN FRANCISCO, CA 94139-9446
PO BOX 399447, SAN FRANCISCO, CA 94139-9447
PO BOX 399448, SAN FRANCISCO, CA 94139-9448
PO BOX 399449, SAN FRANCISCO, CA 94139-9449
PO BOX 399450, SAN FRANCISCO, CA 94139-9450
PO BOX 399451, SAN FRANCISCO, CA 94139-9451
PO BOX 399452, SAN FRANCISCO, CA 94139-9452
PO BOX 399453, SAN FRANCISCO, CA 94139-9453
PO BOX 399454, SAN FRANCISCO, CA 94139-9454
PO BOX 399455, SAN FRANCISCO, CA 94139-9455
PO BOX 399456, SAN FRANCISCO, CA 94139-9456
PO BOX 399457, SAN FRANCISCO, CA 94139-9457
PO BOX 399458, SAN FRANCISCO, CA 94139-9458
PO BOX 399459, SAN FRANCISCO, CA 94139-9459
PO BOX 399460, SAN FRANCISCO, CA 94139-9460
PO BOX 399461, SAN FRANCISCO, CA 94139-9461
PO BOX 399462, SAN FRANCISCO, CA 94139-9462
PO BOX 399463, SAN FRANCISCO, CA 94139-9463
PO BOX 399464, SAN FRANCISCO, CA 94139-9464
PO BOX 399465, SAN FRANCISCO, CA 94139-9465
PO BOX 399466, SAN FRANCISCO, CA 94139-9466
PO BOX 399467, SAN FRANCISCO, CA 94139-9467
PO BOX 399468, SAN FRANCISCO, CA 94139-9468
PO BOX 399469, SAN FRANCISCO, CA 94139-9469
PO BOX 399470, SAN FRANCISCO, CA 94139-9470
PO BOX 399471, SAN FRANCISCO, CA 94139-9471
PO BOX 399472, SAN FRANCISCO, CA 94139-9472
PO BOX 399473, SAN FRANCISCO, CA 94139-9473
PO BOX 399474, SAN FRANCISCO, CA 94139-9474
PO BOX 399475, SAN FRANCISCO, CA 94139-9475