diff --git a/lib/buy_account_credit_form.rb b/lib/buy_account_credit_form.rb
index 69b367672708066cd08fa84cd3f52d57236307a4..367a95933a8fd36683842029c078489e6aa2b1f8 100644
--- a/lib/buy_account_credit_form.rb
+++ b/lib/buy_account_credit_form.rb
@@ -4,10 +4,19 @@ require_relative "trust_level_repo"
 require_relative "credit_card_sale"
 
 class BuyAccountCreditForm
+	# Returns a TrustLevelRepo instance, allowing for dependency injection.
+	# Either creates a new instance given kwargs or returns the existing instance.
+	# @param kwargs [Hash] keyword arguments.
+	# @option kwargs [TrustLevelRepo] :trust_level_repo An existing TrustLevelRepo instance.
+	# @return [TrustLevelRepo] An instance of TrustLevelRepo.
 	def self.trust_level_repo(**kwargs)
 		kwargs[:trust_level_repo] || TrustLevelRepo.new(**kwargs)
 	end
 
+	# Factory method to create a BuyAccountCreditForm for a given customer.
+	# It fetches the customer's trust level to determine the maximum top-up amount.
+	# @param customer [Customer] The customer for whom the form is being created.
+	# @return [EMPromise<BuyAccountCreditForm>] A promise that resolves with the new form instance.
 	def self.for(customer)
 		trust_level_repo.find(customer).then do |trust_level|
 			customer.payment_methods.then do |payment_methods|
@@ -16,12 +25,20 @@ class BuyAccountCreditForm
 		end
 	end
 
+	# Initializes a new BuyAccountCreditForm.
+	# @param balance [BigDecimal] The current balance of the customer.
+	# @param payment_methods [PaymentMethods] The available payment methods for the customer.
+	# @param max_top_up_amount [Numeric] The maximum amount the customer is allowed to top up, based on their trust level.
 	def initialize(balance, payment_methods, max_top_up_amount)
 		@balance = balance
 		@payment_methods = payment_methods
 		@max_top_up_amount = max_top_up_amount
 	end
 
+	# Generates the form template for topping up account credit.
+	# The form will include a range for the amount field, constrained by a minimum of $15
+	# and the customer's specific maximum top-up amount.
+	# @return [FormTemplate::OneRender] The rendered form template.
 	def form
 		FormTemplate.render(
 			:top_up,
diff --git a/lib/credit_card_sale.rb b/lib/credit_card_sale.rb
index eeb830fb9681c4b107a7ff8685eee93d07db4a66..780efcc6cd9995ac318a5dca43455fc2528bd38b 100644
--- a/lib/credit_card_sale.rb
+++ b/lib/credit_card_sale.rb
@@ -8,9 +8,16 @@ require_relative "trust_level_repo"
 
 class TransactionDeclinedError < StandardError; end
 
+# Error raised when a transaction amount exceeds the maximum allowed limit.
 class AmountTooHighError < TransactionDeclinedError
-	attr_reader :amount, :max_amount
-
+	# @return [Numeric] The transaction amount that was too high.
+	attr_reader :amount
+	# @return [Numeric] The maximum amount allowed for the transaction.
+	attr_reader :max_amount
+
+	# Initializes a new AmountTooHighError.
+	# @param amount [Numeric] The transaction amount.
+	# @param max_amount [Numeric] The maximum allowed amount.
 	def initialize(amount, max_amount)
 		@amount = amount
 		@max_amount = max_amount
@@ -18,9 +25,16 @@ class AmountTooHighError < TransactionDeclinedError
 	end
 end
 
+# Error raised when a transaction amount is below the minimum required limit.
 class AmountTooLowError < TransactionDeclinedError
-	attr_reader :amount, :min_amount
-
+	# @return [Numeric] The transaction amount that was too low.
+	attr_reader :amount
+	# @return [Numeric] The minimum amount required for the transaction.
+	attr_reader :min_amount
+
+	# Initializes a new AmountTooLowError.
+	# @param amount [Numeric] The transaction amount.
+	# @param min_amount [Numeric] The minimum required amount.
 	def initialize(amount, min_amount)
 		@amount = amount
 		@min_amount = min_amount
@@ -28,9 +42,16 @@ class AmountTooLowError < TransactionDeclinedError
 	end
 end
 
+# Error raised when a transaction is declined, potentially due to exceeding decline limits.
 class DeclinedError < TransactionDeclinedError
-	attr_reader :declines, :max_declines
-
+	# @return [Integer, nil] The number of declines the customer has.
+	attr_reader :declines
+	# @return [Integer, nil] The maximum number of declines allowed.
+	attr_reader :max_declines
+
+	# Initializes a new DeclinedError.
+	# @param declines [Integer, nil] The current number of declines.
+	# @param max_declines [Integer, nil] The maximum allowed declines.
 	def initialize(declines, max_declines)
 		@declines = declines
 		@max_declines = max_declines
@@ -89,6 +110,12 @@ class CreditCardSale
 
 protected
 
+	# Validates the transaction against customer locks, trust level, and decline history.
+	# @raise [TransactionDeclinedError] if the customer has made too many payments recently.
+	# @raise [AmountTooHighError] if the amount exceeds the trust level's maximum top-up amount.
+	# @raise [AmountTooLowError] if the amount is below any applicable minimum.
+	# @raise [DeclinedError] if the transaction is declined due to too many previous declines or other trust level restrictions.
+	# @return [EMPromise<void>] A promise that resolves if validation passes, or rejects with an error.
 	def validate!
 		EMPromise.all([
 			REDIS.exists("jmp_customer_credit_card_lock-#{@customer.customer_id}"),
diff --git a/lib/trust_level.rb b/lib/trust_level.rb
index 7db31271943fcd366a0986c6af9bf2e5785d9d3a..cb48bf39a62dc3afcdcb9a3fd9d6c3a0c2e30251 100644
--- a/lib/trust_level.rb
+++ b/lib/trust_level.rb
@@ -32,6 +32,8 @@ module TrustLevel
 			new if manual == "Tomb"
 		end
 
+		# The maximum amount a user at Tomb trust level can top up.
+		# @return [Integer] Always 0 for Tomb level.
 		def max_top_up_amount
 			0
 		end
@@ -48,6 +50,11 @@ module TrustLevel
 			false
 		end
 
+		# Validates a credit card transaction for a Tomb trust level user.
+		# Users at this level cannot make credit card transactions.
+		# @param _amount [BigDecimal] The amount of the transaction (ignored).
+		# @param _declines [Integer] The number of recent declines (ignored).
+		# @raise [DeclinedError] Always raised to prevent transactions.
 		def validate_credit_card_transaction!(_amount, _declines)
 			# Give a more ambiguous error so they don't know they're tombed.
 			raise DeclinedError
@@ -67,10 +74,15 @@ module TrustLevel
 			new if manual == "Basement" || (!manual && settled_amount < 10)
 		end
 
+		# The maximum amount a user at Basement trust level can top up.
+		# @return [Integer]
 		def max_top_up_amount
 			35
 		end
 
+		# The maximum number of credit card declines allowed for a Basement user
+		# before further transactions are blocked.
+		# @return [Integer]
 		def max_declines
 			2
 		end
@@ -87,6 +99,11 @@ module TrustLevel
 			messages_today < 40
 		end
 
+		# Validates a credit card transaction for a Basement trust level user.
+		# @param amount [BigDecimal] The amount of the transaction.
+		# @param declines [Integer] The number of recent declines for the customer.
+		# @raise [DeclinedError] if the number of declines exceeds `max_declines`.
+		# @raise [AmountTooHighError] if the transaction amount exceeds `max_top_up_amount`.
 		def validate_credit_card_transaction!(amount, declines)
 			raise DeclinedError.new(declines, max_declines) if declines > max_declines
 			return unless amount > max_top_up_amount
@@ -108,10 +125,15 @@ module TrustLevel
 			new if manual == "Paragon" || (!manual && settled_amount > 60)
 		end
 
+		# The maximum amount a user at Paragon trust level can top up.
+		# @return [Integer]
 		def max_top_up_amount
 			500
 		end
 
+		# The maximum number of credit card declines allowed for a Paragon user
+		# before further transactions are blocked.
+		# @return [Integer]
 		def max_declines
 			3
 		end
@@ -128,6 +150,11 @@ module TrustLevel
 			messages_today < 700
 		end
 
+		# Validates a credit card transaction for a Paragon trust level user.
+		# @param amount [BigDecimal] The amount of the transaction.
+		# @param declines [Integer] The number of recent declines for the customer.
+		# @raise [DeclinedError] if the number of declines exceeds `max_declines`.
+		# @raise [AmountTooHighError] if the transaction amount exceeds `max_top_up_amount`.
 		def validate_credit_card_transaction!(amount, declines)
 			raise DeclinedError.new(declines, max_declines) if declines > max_declines
 			return unless amount > max_top_up_amount
@@ -161,6 +188,11 @@ module TrustLevel
 			true
 		end
 
+		# Validates a credit card transaction for an Olympias trust level user.
+		# Users at this level have no restrictions on credit card transactions through this method.
+		# @param _amount [BigDecimal] The amount of the transaction (ignored).
+		# @param _declines [Integer] The number of recent declines (ignored).
+		# @return [void]
 		def validate_credit_card_transaction!(*) end
 
 		def create_subaccount?(*)
@@ -192,10 +224,15 @@ module TrustLevel
 			@max_rate = EXPENSIVE_ROUTE.fetch(plan_name, 0.1)
 		end
 
+		# The maximum amount a user at Customer trust level can top up.
+		# @return [Integer]
 		def max_top_up_amount
 			130
 		end
 
+		# The maximum number of credit card declines allowed for a Customer user
+		# before further transactions are blocked.
+		# @return [Integer]
 		def max_declines
 			2
 		end
@@ -212,6 +249,11 @@ module TrustLevel
 			messages_today < 500
 		end
 
+		# Validates a credit card transaction for a Customer trust level user.
+		# @param amount [BigDecimal] The amount of the transaction.
+		# @param declines [Integer] The number of recent declines for the customer.
+		# @raise [DeclinedError] if the number of declines exceeds `max_declines`.
+		# @raise [AmountTooHighError] if the transaction amount exceeds `max_top_up_amount`.
 		def validate_credit_card_transaction!(amount, declines)
 			raise DeclinedError.new(declines, max_declines) if declines > max_declines
 			return unless amount > max_top_up_amount