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 901, SAN MARCOS, CA 92079-0901
PO BOX 902, SAN MARCOS, CA 92079-0902
PO BOX 903, SAN MARCOS, CA 92079-0903
PO BOX 904, SAN MARCOS, CA 92079-0904
PO BOX 905, SAN MARCOS, CA 92079-0905
PO BOX 906, SAN MARCOS, CA 92079-0906
PO BOX 907, SAN MARCOS, CA 92079-0907
PO BOX 908, SAN MARCOS, CA 92079-0908
PO BOX 909, SAN MARCOS, CA 92079-0909
PO BOX 910, SAN MARCOS, CA 92079-0910
PO BOX 911, SAN MARCOS, CA 92079-0911
PO BOX 912, SAN MARCOS, CA 92079-0912
PO BOX 913, SAN MARCOS, CA 92079-0913
PO BOX 914, SAN MARCOS, CA 92079-0914
PO BOX 915, SAN MARCOS, CA 92079-0915
PO BOX 916, SAN MARCOS, CA 92079-0916
PO BOX 917, SAN MARCOS, CA 92079-0917
PO BOX 918, SAN MARCOS, CA 92079-0918
PO BOX 919, SAN MARCOS, CA 92079-0919
PO BOX 920, SAN MARCOS, CA 92079-0920
PO BOX 921, SAN MARCOS, CA 92079-0921
PO BOX 922, SAN MARCOS, CA 92079-0922
PO BOX 923, SAN MARCOS, CA 92079-0923
PO BOX 924, SAN MARCOS, CA 92079-0924
PO BOX 925, SAN MARCOS, CA 92079-0925
PO BOX 926, SAN MARCOS, CA 92079-0926
PO BOX 927, SAN MARCOS, CA 92079-0927
PO BOX 928, SAN MARCOS, CA 92079-0928
PO BOX 929, SAN MARCOS, CA 92079-0929
PO BOX 930, SAN MARCOS, CA 92079-0930
PO BOX 931, SAN MARCOS, CA 92079-0931
PO BOX 932, SAN MARCOS, CA 92079-0932
PO BOX 933, SAN MARCOS, CA 92079-0933
PO BOX 934, SAN MARCOS, CA 92079-0934
PO BOX 935, SAN MARCOS, CA 92079-0935
PO BOX 936, SAN MARCOS, CA 92079-0936
PO BOX 937, SAN MARCOS, CA 92079-0937
PO BOX 938, SAN MARCOS, CA 92079-0938
PO BOX 939, SAN MARCOS, CA 92079-0939
PO BOX 940, SAN MARCOS, CA 92079-0940
PO BOX 941, SAN MARCOS, CA 92079-0941
PO BOX 942, SAN MARCOS, CA 92079-0942
PO BOX 943, SAN MARCOS, CA 92079-0943
PO BOX 944, SAN MARCOS, CA 92079-0944
PO BOX 945, SAN MARCOS, CA 92079-0945
PO BOX 946, SAN MARCOS, CA 92079-0946
PO BOX 947, SAN MARCOS, CA 92079-0947
PO BOX 948, SAN MARCOS, CA 92079-0948
PO BOX 949, SAN MARCOS, CA 92079-0949
PO BOX 950, SAN MARCOS, CA 92079-0950
PO BOX 951, SAN MARCOS, CA 92079-0951
PO BOX 952, SAN MARCOS, CA 92079-0952
PO BOX 953, SAN MARCOS, CA 92079-0953
PO BOX 954, SAN MARCOS, CA 92079-0954
PO BOX 955, SAN MARCOS, CA 92079-0955
PO BOX 956, SAN MARCOS, CA 92079-0956
PO BOX 957, SAN MARCOS, CA 92079-0957
PO BOX 958, SAN MARCOS, CA 92079-0958
PO BOX 959, SAN MARCOS, CA 92079-0959
PO BOX 960, SAN MARCOS, CA 92079-0960
PO BOX 961, SAN MARCOS, CA 92079-0961
PO BOX 962, SAN MARCOS, CA 92079-0962
PO BOX 963, SAN MARCOS, CA 92079-0963
PO BOX 964, SAN MARCOS, CA 92079-0964
PO BOX 965, SAN MARCOS, CA 92079-0965
PO BOX 966, SAN MARCOS, CA 92079-0966
PO BOX 967, SAN MARCOS, CA 92079-0967
PO BOX 968, SAN MARCOS, CA 92079-0968
PO BOX 969, SAN MARCOS, CA 92079-0969
PO BOX 970, SAN MARCOS, CA 92079-0970
PO BOX 971, SAN MARCOS, CA 92079-0971
PO BOX 972, SAN MARCOS, CA 92079-0972
PO BOX 973, SAN MARCOS, CA 92079-0973
PO BOX 974, SAN MARCOS, CA 92079-0974
PO BOX 975, SAN MARCOS, CA 92079-0975
PO BOX 976, SAN MARCOS, CA 92079-0976
PO BOX 977, SAN MARCOS, CA 92079-0977
PO BOX 978, SAN MARCOS, CA 92079-0978
PO BOX 979, SAN MARCOS, CA 92079-0979
PO BOX 980, SAN MARCOS, CA 92079-0980
PO BOX 981, SAN MARCOS, CA 92079-0981
PO BOX 982, SAN MARCOS, CA 92079-0982
PO BOX 983, SAN MARCOS, CA 92079-0983
PO BOX 984, SAN MARCOS, CA 92079-0984
PO BOX 985, SAN MARCOS, CA 92079-0985
PO BOX 986, SAN MARCOS, CA 92079-0986
PO BOX 987, SAN MARCOS, CA 92079-0987
PO BOX 988, SAN MARCOS, CA 92079-0988
PO BOX 989, SAN MARCOS, CA 92079-0989
PO BOX 990, SAN MARCOS, CA 92079-0990
PO BOX 991, SAN MARCOS, CA 92079-0991
PO BOX 992, SAN MARCOS, CA 92079-0992
PO BOX 993, SAN MARCOS, CA 92079-0993
PO BOX 994, SAN MARCOS, CA 92079-0994
PO BOX 995, SAN MARCOS, CA 92079-0995
PO BOX 996, SAN MARCOS, CA 92079-0996
PO BOX 997, SAN MARCOS, CA 92079-0997
PO BOX 998, SAN MARCOS, CA 92079-0998
PO BOX 999, SAN MARCOS, CA 92079-0999
PO BOX 1000, SAN MARCOS, CA 92079-1000
PO BOX 1001, SAN MARCOS, CA 92079-1001
PO BOX 1002, SAN MARCOS, CA 92079-1002
PO BOX 1003, SAN MARCOS, CA 92079-1003
PO BOX 1004, SAN MARCOS, CA 92079-1004
PO BOX 1005, SAN MARCOS, CA 92079-1005
PO BOX 1006, SAN MARCOS, CA 92079-1006
PO BOX 1007, SAN MARCOS, CA 92079-1007
PO BOX 1008, SAN MARCOS, CA 92079-1008
PO BOX 1009, SAN MARCOS, CA 92079-1009
PO BOX 1010, SAN MARCOS, CA 92079-1010
PO BOX 1011, SAN MARCOS, CA 92079-1011
PO BOX 1012, SAN MARCOS, CA 92079-1012
PO BOX 1013, SAN MARCOS, CA 92079-1013
PO BOX 1014, SAN MARCOS, CA 92079-1014
PO BOX 1015, SAN MARCOS, CA 92079-1015
PO BOX 1016, SAN MARCOS, CA 92079-1016
PO BOX 1017, SAN MARCOS, CA 92079-1017
PO BOX 1018, SAN MARCOS, CA 92079-1018
PO BOX 1019, SAN MARCOS, CA 92079-1019
PO BOX 1020, SAN MARCOS, CA 92079-1020
PO BOX 1021, SAN MARCOS, CA 92079-1021
PO BOX 1022, SAN MARCOS, CA 92079-1022
PO BOX 1023, SAN MARCOS, CA 92079-1023
PO BOX 1024, SAN MARCOS, CA 92079-1024
PO BOX 1025, SAN MARCOS, CA 92079-1025
PO BOX 1026, SAN MARCOS, CA 92079-1026
PO BOX 1027, SAN MARCOS, CA 92079-1027
PO BOX 1028, SAN MARCOS, CA 92079-1028
PO BOX 1029, SAN MARCOS, CA 92079-1029
PO BOX 1030, SAN MARCOS, CA 92079-1030
PO BOX 1031, SAN MARCOS, CA 92079-1031
PO BOX 1032, SAN MARCOS, CA 92079-1032
PO BOX 1033, SAN MARCOS, CA 92079-1033
PO BOX 1034, SAN MARCOS, CA 92079-1034
PO BOX 1035, SAN MARCOS, CA 92079-1035
PO BOX 1036, SAN MARCOS, CA 92079-1036
PO BOX 1037, SAN MARCOS, CA 92079-1037
PO BOX 1038, SAN MARCOS, CA 92079-1038
PO BOX 1039, SAN MARCOS, CA 92079-1039
PO BOX 1040, SAN MARCOS, CA 92079-1040
PO BOX 1041, SAN MARCOS, CA 92079-1041
PO BOX 1042, SAN MARCOS, CA 92079-1042
PO BOX 1043, SAN MARCOS, CA 92079-1043
PO BOX 1044, SAN MARCOS, CA 92079-1044
PO BOX 1045, SAN MARCOS, CA 92079-1045
PO BOX 1046, SAN MARCOS, CA 92079-1046
PO BOX 1047, SAN MARCOS, CA 92079-1047
PO BOX 1048, SAN MARCOS, CA 92079-1048
PO BOX 1049, SAN MARCOS, CA 92079-1049
PO BOX 1050, SAN MARCOS, CA 92079-1050
PO BOX 1051, SAN MARCOS, CA 92079-1051
PO BOX 1052, SAN MARCOS, CA 92079-1052
PO BOX 1053, SAN MARCOS, CA 92079-1053
PO BOX 1054, SAN MARCOS, CA 92079-1054
PO BOX 1055, SAN MARCOS, CA 92079-1055
PO BOX 1056, SAN MARCOS, CA 92079-1056
PO BOX 1057, SAN MARCOS, CA 92079-1057
PO BOX 1058, SAN MARCOS, CA 92079-1058
PO BOX 1059, SAN MARCOS, CA 92079-1059
PO BOX 1060, SAN MARCOS, CA 92079-1060
PO BOX 1061, SAN MARCOS, CA 92079-1061
PO BOX 1062, SAN MARCOS, CA 92079-1062
PO BOX 1063, SAN MARCOS, CA 92079-1063
PO BOX 1064, SAN MARCOS, CA 92079-1064
PO BOX 1065, SAN MARCOS, CA 92079-1065
PO BOX 1066, SAN MARCOS, CA 92079-1066
PO BOX 1067, SAN MARCOS, CA 92079-1067
PO BOX 1068, SAN MARCOS, CA 92079-1068
PO BOX 1069, SAN MARCOS, CA 92079-1069
PO BOX 1070, SAN MARCOS, CA 92079-1070
PO BOX 1071, SAN MARCOS, CA 92079-1071
PO BOX 1072, SAN MARCOS, CA 92079-1072
PO BOX 1073, SAN MARCOS, CA 92079-1073
PO BOX 1074, SAN MARCOS, CA 92079-1074
PO BOX 1075, SAN MARCOS, CA 92079-1075
PO BOX 1076, SAN MARCOS, CA 92079-1076
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