Mailing Address Requirements

These formatting rules apply to any mailing processed through Checkissuing. Meeting them prevents delays and delivery failures.

They govern the address, address2, city, state, zip, country, mail_to, and recipient_instructions fields documented on the Payment Fields page. Character limits vary by postage type — see the Postage Types page for the code you're sending.

Character limits by mail type

Each address line (mail_to, recipient_instructions, address, address2) must not exceed the following character limits:

Mail type Postage codes Max characters per line PO boxes permitted?
FedEx 1C, FFO, FPO, FSD, SC 35 No — street address required
UPS — 35 No — street address required
USPS (First Class, Priority, Priority Express, Certified) FC, PR, PRS, USPSCERT 46 Yes

General requirements — all mail types

  • address (Address line 1) must contain a deliverable street address or PO box.
  • Attention lines, suite/apartment numbers, and company names belong in address2 (Address line 2). They may alternatively be prepended to address only if the combined value stays within the applicable character limit for your mail type.
  • city is required.
  • state is required — use the 2-letter USPS abbreviation only (e.g. CA, TX, NY).
  • zip is required — 5-digit format (e.g. 12345) or ZIP+4 format (e.g. 12345-6789).
  • International mailings must include country as a dedicated field using a 2-letter ISO country code (e.g. CA, MX, GB).
  • Do not embed the country name in any free-form address line. The country field applies to international mailings only and should be omitted on domestic addresses.