USPS 421 Window Clerk Exam Study
Guide 2025: Expert-Verified Answers
& Practice Test
Question 1: A customer requests to send a package via Priority Mail Express. What is the
maximum weight allowed for this service? A. 50 lbs B. 70 lbs C. 100 lbs D. 130 lbs
Correct Answer: B Rationale: Priority Mail Express allows packages up to 70 lbs. Priority Mail
(A) also allows up to 70 lbs, but the question specifies Priority Mail Express. First-Class Mail (not
listed) has a lower limit, and 100 lbs (C) and 130 lbs (D) exceed USPS weight limits for this
service.
Question 2: A customer wants to mail a letter to Canada. Which USPS service provides the
fastest delivery? A. First-Class Mail International B. Priority Mail International C. Priority Mail
Express International D. Global Express Guaranteed
Correct Answer: D Rationale: Global Express Guaranteed is the fastest USPS international
service, with delivery in 1–3 business days. Priority Mail Express International (C) is fast but not
as quick as Global Express Guaranteed. Priority Mail International (B) and First-Class Mail
International (A) are slower options.
Question 3: A customer purchases $50 in stamps using a credit card. What is the correct
procedure for processing this transaction? A. Swipe the card, print the receipt, and give the
stamps without verification B. Swipe the card, verify the signature, and provide the stamps and
receipt C. Manually enter the card number and provide the stamps without a receipt D. Accept
cash only for stamp purchases over $20
Correct Answer: B Rationale: For credit card transactions, USPS policy requires swiping
the card, verifying the signature , and providing a receipt along with the stamps. Option A
omits signature verification, C is incorrect because manual entry is not standard for in-person
transactions, and D is false—credit cards are accepted for any amount.
,Question 4: A customer brings in a package with a live scorpion inside for mailing. What should
the clerk do? A. Accept the package with a "Fragile" sticker B. Refuse the package and explain
that live scorpions are prohibited C. Charge extra for hazardous material handling D. Accept the
package but require a signature from the customer
Correct Answer: B Rationale: Live scorpions are prohibited by USPS regulations. The clerk
must refuse the package and inform the customer. Accepting the package (A, D) or charging
extra (C) violates USPS policies.
Question 5: A customer wants to purchase a money order for $500. What form of payment is
NOT acceptable for this transaction? A. Cash B. Debit card C. Personal check D. Credit card
Correct Answer: C Rationale: USPS does not accept personal checks for money order
purchases. Cash (A), debit cards (B), and credit cards (D) are all acceptable forms of payment.
Question 6: A customer requests a Certified Mail receipt. What must the clerk do to complete
this transaction? A. Provide a handwritten receipt B. Print a PS Form 3800 and attach it to the
mailpiece C. Stamp the envelope with "Certified Mail" D. Charge an additional fee for tracking
Correct Answer: B Rationale: For Certified Mail, the clerk must print and attach PS Form
3800 to the mailpiece. A handwritten receipt (A) is insufficient, stamping (C) does not replace the
form, and while there is a fee (D), the form is still required.
Question 7: A customer is shipping a package containing lithium batteries. What is the correct
procedure? A. Refuse the package, as lithium batteries are prohibited B. Accept the package if
the batteries are installed in equipment C. Charge a hazardous material fee D. Require the
customer to sign a liability waiver
Correct Answer: B Rationale: Lithium batteries installed in equipment are permitted under
USPS regulations, provided they meet specific criteria. Refusing the package (A) is incorrect
unless the batteries are loose or non-compliant. Charging a fee (C) or requiring a waiver (D) is
not standard procedure.
Question 8: A customer wants to mail a package to a military address (APO/FPO). Which
USPS service is NOT available for this destination? A. Priority Mail B. First-Class Mail C. Priority
Mail Express D. Media Mail
,Correct Answer: D Rationale: Media Mail is not available for APO/FPO addresses. Priority
Mail (A), First-Class Mail (B), and Priority Mail Express (C) are all valid options for military
addresses.
Question 9: A customer requests a return receipt for a Certified Mail letter. What is the
additional fee for this service? A. $1.25 B. $2.85 C. $3.50 D. $4.95
Correct Answer: B Rationale: The fee for a return receipt for Certified Mail is $2.85. The other
options ($1.25, $3.50, $4.95) are incorrect as of USPS pricing guidelines.
Question 10: A customer brings in a package with insufficient postage. The clerk notices the
package is also improperly sealed. What should the clerk do? A. Accept the package as-is and
charge the customer for additional postage B. Refuse the package due to improper sealing C.
Reseal the package, add postage, and accept it D. Accept the package but note the improper
sealing on the receipt
Correct Answer: B Rationale: USPS regulations require packages to be properly sealed. If a
package is improperly sealed, the clerk must refuse it. Accepting the package (A, C, D) would
violate USPS policies.
Question 11: A customer wants to mail a package that exceeds the size limit for Priority Mail.
What is the maximum combined length and girth for Priority Mail? A. 84 inches B. 108 inches C.
130 inches D. 165 inches
Correct Answer: B Rationale: The maximum combined length and girth for Priority Mail is
108 inches. The other options (84, 130, 165 inches) do not match USPS size regulations.
Question 12: A customer requests a signature confirmation for a package. What is the fee for
this service? A. $1.25 B. $2.85 C. $3.50 D. $4.95
Correct Answer: C Rationale: The fee for Signature Confirmation is $3.50. The other options
($1.25, $2.85, $4.95) are incorrect as of USPS pricing.
Question 13: A customer wants to ship a package containing perfume. What is the correct
procedure? A. Refuse the package, as perfume is prohibited B. Accept the package if it is
properly sealed and labeled C. Charge a hazardous material fee D. Require the customer to sign
a liability waiver
, Correct Answer: B Rationale: Perfume is permitted if it is non-flammable and properly
sealed and labeled. Refusing the package (A) is incorrect unless it violates USPS regulations.
Charging a fee (C) or requiring a waiver (D) is not standard procedure.
Question 14: A customer wants to mail a letter using First-Class Mail. What is the maximum
weight for a First-Class Mail letter? A. 12 ounces B. 13 ounces C. 15.994 ounces D. 16 ounces
Correct Answer: B Rationale: The maximum weight for a First-Class Mail letter is 13 ounces.
The other options (12, 15.994, 16 ounces) are incorrect.
Question 15: A customer wants to purchase postage for a package but does not know the
exact weight. What should the clerk do? A. Estimate the weight and charge accordingly B.
Weigh the package and calculate the postage C. Refuse to sell postage without an exact weight
D. Charge the customer for the heaviest weight category
Correct Answer: B Rationale: The clerk must weigh the package to determine the accurate
postage . Estimating (A) or charging for the heaviest category (D) could result in incorrect
postage. Refusing service (C) is not customer-friendly or necessary.
Question 16: A customer wants to mail a package to Puerto Rico. Which USPS service treats
Puerto Rico as a domestic destination? A. First-Class Package Service B. Priority Mail C.
Priority Mail Express D. All of the above
Correct Answer: D Rationale: Puerto Rico is considered a domestic destination for all
USPS services, including First-Class Package Service (A), Priority Mail (B), and Priority Mail
Express (C).
Question 17: A customer requests a change of address. What form must the customer
complete? A. PS Form 3575 B. PS Form 3800 C. PS Form 8125 D. PS Form 1093
Correct Answer: A Rationale: The correct form for a change of address is PS Form 3575.
PS Form 3800 (B) is for Certified Mail, PS Form 8125 (C) is for money orders, and PS Form
1093 (D) is for postal inspections.
Question 18: A customer wants to mail a package containing dry ice. What is the maximum
amount of dry ice allowed per package? A. 2.5 lbs B. 5.5 lbs C. 10 lbs D. 15 lbs
Guide 2025: Expert-Verified Answers
& Practice Test
Question 1: A customer requests to send a package via Priority Mail Express. What is the
maximum weight allowed for this service? A. 50 lbs B. 70 lbs C. 100 lbs D. 130 lbs
Correct Answer: B Rationale: Priority Mail Express allows packages up to 70 lbs. Priority Mail
(A) also allows up to 70 lbs, but the question specifies Priority Mail Express. First-Class Mail (not
listed) has a lower limit, and 100 lbs (C) and 130 lbs (D) exceed USPS weight limits for this
service.
Question 2: A customer wants to mail a letter to Canada. Which USPS service provides the
fastest delivery? A. First-Class Mail International B. Priority Mail International C. Priority Mail
Express International D. Global Express Guaranteed
Correct Answer: D Rationale: Global Express Guaranteed is the fastest USPS international
service, with delivery in 1–3 business days. Priority Mail Express International (C) is fast but not
as quick as Global Express Guaranteed. Priority Mail International (B) and First-Class Mail
International (A) are slower options.
Question 3: A customer purchases $50 in stamps using a credit card. What is the correct
procedure for processing this transaction? A. Swipe the card, print the receipt, and give the
stamps without verification B. Swipe the card, verify the signature, and provide the stamps and
receipt C. Manually enter the card number and provide the stamps without a receipt D. Accept
cash only for stamp purchases over $20
Correct Answer: B Rationale: For credit card transactions, USPS policy requires swiping
the card, verifying the signature , and providing a receipt along with the stamps. Option A
omits signature verification, C is incorrect because manual entry is not standard for in-person
transactions, and D is false—credit cards are accepted for any amount.
,Question 4: A customer brings in a package with a live scorpion inside for mailing. What should
the clerk do? A. Accept the package with a "Fragile" sticker B. Refuse the package and explain
that live scorpions are prohibited C. Charge extra for hazardous material handling D. Accept the
package but require a signature from the customer
Correct Answer: B Rationale: Live scorpions are prohibited by USPS regulations. The clerk
must refuse the package and inform the customer. Accepting the package (A, D) or charging
extra (C) violates USPS policies.
Question 5: A customer wants to purchase a money order for $500. What form of payment is
NOT acceptable for this transaction? A. Cash B. Debit card C. Personal check D. Credit card
Correct Answer: C Rationale: USPS does not accept personal checks for money order
purchases. Cash (A), debit cards (B), and credit cards (D) are all acceptable forms of payment.
Question 6: A customer requests a Certified Mail receipt. What must the clerk do to complete
this transaction? A. Provide a handwritten receipt B. Print a PS Form 3800 and attach it to the
mailpiece C. Stamp the envelope with "Certified Mail" D. Charge an additional fee for tracking
Correct Answer: B Rationale: For Certified Mail, the clerk must print and attach PS Form
3800 to the mailpiece. A handwritten receipt (A) is insufficient, stamping (C) does not replace the
form, and while there is a fee (D), the form is still required.
Question 7: A customer is shipping a package containing lithium batteries. What is the correct
procedure? A. Refuse the package, as lithium batteries are prohibited B. Accept the package if
the batteries are installed in equipment C. Charge a hazardous material fee D. Require the
customer to sign a liability waiver
Correct Answer: B Rationale: Lithium batteries installed in equipment are permitted under
USPS regulations, provided they meet specific criteria. Refusing the package (A) is incorrect
unless the batteries are loose or non-compliant. Charging a fee (C) or requiring a waiver (D) is
not standard procedure.
Question 8: A customer wants to mail a package to a military address (APO/FPO). Which
USPS service is NOT available for this destination? A. Priority Mail B. First-Class Mail C. Priority
Mail Express D. Media Mail
,Correct Answer: D Rationale: Media Mail is not available for APO/FPO addresses. Priority
Mail (A), First-Class Mail (B), and Priority Mail Express (C) are all valid options for military
addresses.
Question 9: A customer requests a return receipt for a Certified Mail letter. What is the
additional fee for this service? A. $1.25 B. $2.85 C. $3.50 D. $4.95
Correct Answer: B Rationale: The fee for a return receipt for Certified Mail is $2.85. The other
options ($1.25, $3.50, $4.95) are incorrect as of USPS pricing guidelines.
Question 10: A customer brings in a package with insufficient postage. The clerk notices the
package is also improperly sealed. What should the clerk do? A. Accept the package as-is and
charge the customer for additional postage B. Refuse the package due to improper sealing C.
Reseal the package, add postage, and accept it D. Accept the package but note the improper
sealing on the receipt
Correct Answer: B Rationale: USPS regulations require packages to be properly sealed. If a
package is improperly sealed, the clerk must refuse it. Accepting the package (A, C, D) would
violate USPS policies.
Question 11: A customer wants to mail a package that exceeds the size limit for Priority Mail.
What is the maximum combined length and girth for Priority Mail? A. 84 inches B. 108 inches C.
130 inches D. 165 inches
Correct Answer: B Rationale: The maximum combined length and girth for Priority Mail is
108 inches. The other options (84, 130, 165 inches) do not match USPS size regulations.
Question 12: A customer requests a signature confirmation for a package. What is the fee for
this service? A. $1.25 B. $2.85 C. $3.50 D. $4.95
Correct Answer: C Rationale: The fee for Signature Confirmation is $3.50. The other options
($1.25, $2.85, $4.95) are incorrect as of USPS pricing.
Question 13: A customer wants to ship a package containing perfume. What is the correct
procedure? A. Refuse the package, as perfume is prohibited B. Accept the package if it is
properly sealed and labeled C. Charge a hazardous material fee D. Require the customer to sign
a liability waiver
, Correct Answer: B Rationale: Perfume is permitted if it is non-flammable and properly
sealed and labeled. Refusing the package (A) is incorrect unless it violates USPS regulations.
Charging a fee (C) or requiring a waiver (D) is not standard procedure.
Question 14: A customer wants to mail a letter using First-Class Mail. What is the maximum
weight for a First-Class Mail letter? A. 12 ounces B. 13 ounces C. 15.994 ounces D. 16 ounces
Correct Answer: B Rationale: The maximum weight for a First-Class Mail letter is 13 ounces.
The other options (12, 15.994, 16 ounces) are incorrect.
Question 15: A customer wants to purchase postage for a package but does not know the
exact weight. What should the clerk do? A. Estimate the weight and charge accordingly B.
Weigh the package and calculate the postage C. Refuse to sell postage without an exact weight
D. Charge the customer for the heaviest weight category
Correct Answer: B Rationale: The clerk must weigh the package to determine the accurate
postage . Estimating (A) or charging for the heaviest category (D) could result in incorrect
postage. Refusing service (C) is not customer-friendly or necessary.
Question 16: A customer wants to mail a package to Puerto Rico. Which USPS service treats
Puerto Rico as a domestic destination? A. First-Class Package Service B. Priority Mail C.
Priority Mail Express D. All of the above
Correct Answer: D Rationale: Puerto Rico is considered a domestic destination for all
USPS services, including First-Class Package Service (A), Priority Mail (B), and Priority Mail
Express (C).
Question 17: A customer requests a change of address. What form must the customer
complete? A. PS Form 3575 B. PS Form 3800 C. PS Form 8125 D. PS Form 1093
Correct Answer: A Rationale: The correct form for a change of address is PS Form 3575.
PS Form 3800 (B) is for Certified Mail, PS Form 8125 (C) is for money orders, and PS Form
1093 (D) is for postal inspections.
Question 18: A customer wants to mail a package containing dry ice. What is the maximum
amount of dry ice allowed per package? A. 2.5 lbs B. 5.5 lbs C. 10 lbs D. 15 lbs
