New Order

New Order Single message format and fields.

New Order

Submit new orders as New Order Single with MsgType (35) set to D.

Identity Mapping

Paxos API Field	FIX Tag
customer_id	Account (1)
profile_id	ClientID (109)

Key Field Rules

• Account (1) is your Paxos customer_id and ClientID (109) is your Paxos profile_id.
• Price (44) must be omitted for Market (1) and Stop Market (3) orders.
• CashOrderQty (152) is required for market buy orders and represents the fiat notional to convert.
• OrderQty (38) is required for market sell, stop market sell, stop limit sell, and all limit orders.
• Send only one of OrderQty (38) or CashOrderQty (152).
• StopPx (99) is required for stop market and stop limit orders. Currently only sell stop loss orders are supported.
• HandlInst (21) must be set to 1.
• Symbol (55) must be the currency pair, and SecurityType (167) must be FOR.

Supported Order Types

We support the following OrdType (40) values:

Order type	OrdType (40)
Market	1
Limit	2
Stop Market	3
Stop Limit	4

Post-only orders are Limit (2) orders with ExecInst (18) set to 6 (Post-Only).

Time In Force

Time in force is set with TimeInForce (59):

TimeInForce (59)	Meaning
1	Good Till Cancel (GTC)
3	Immediate or Cancel (IOC)
4	Fill or Kill (FOK)
6	Good Till Time (GTT)

Order type (OrdType 40)	Allowed TimeInForce (59)	Default
Limit (2)	1, 3, 4, 6	1 (GTC)
Market (1)	3	3 (IOC)
Stop Market (3)	1, 6	1 (GTC)
Stop Limit (4)	1, 6	1 (GTC)

For GTT (6), include ExpireTime (126) in YYYYMMDD-HH:MM:SS or YYYYMMDD-HH:MM:SS.sss (milliseconds are ignored).

Tick Size Requirements

Price (44) must align to market tick sizes for limit and stop limit orders:

Market	Tick size	Requirement
XBT markets	0.25	Price (44) must be evenly divisible by 0.25
ETH markets	0.05	Price (44) must be evenly divisible by 0.05
All other markets	0.01	Price (44) must be evenly divisible by 0.01

Maximum Notional Order Size By Type

Maximum notional limits are based on OrdType (40):

Order type (OrdType 40)	Markets	Max notional (USD)
Limit (2)	XBTUSD, ETHUSD	1,500,000
Limit (2)	All other markets	1,000,000
Market (1)	All	500,000

Limit Order Taker Price Protection

Limit orders will be rejected if the order is taker and the Price (44) deviates by 15% or more from the midpoint.

For FIX/GFIX inbound orders, this rejection is returned as an Execution Report with:

• Text (58) = InvalidPriceForTakerOrder
• OrdRejReason (103) = 0 (Broker option)

See Execution Report - Order Reject for the full response format.

Message Format – Outgoing Message

Standard FIX Fields (All Order Types)

Tag	Field	When to Include	Notes
8	BeginString	Always	Standard FIX header
9	BodyLength	Always	Standard FIX header
35	MsgType	Always	D (New Order Single)
49	SenderCompID	Always	Standard FIX header
56	TargetCompID	Always	Standard FIX header
34	MsgSeqNum	Always	Standard FIX header
52	SendingTime	Always	Standard FIX header

Standard FIX Trailer

Tag	Field	When to Include	Notes
10	CheckSum	Always

Common Order Fields (All Order Types)

Tag	Field	When to Include	Notes
11	ClOrdID	Always	Client order ID (a-z, A-Z, 0-9, ., -, _, $, :)
109	ClientID	Always	Paxos profile_id
1	Account	Always	Paxos customer_id
21	HandlInst	Always	Must be 1
55	Symbol	Always	Currency pair
167	SecurityType	Always	Must be FOR
54	Side	Always	1 = Buy, 2 = Sell
60	TransactTime	Always

Market

Set OrdType (40) to 1 (Market). Price (44) must be omitted. See Time In Force and Maximum Notional Order Size By Type.

Required

Tag	Field	When to Include	Notes
40	OrdType	Always	1 (Market)

Conditional

Tag	Field	When to Include	Notes
152	CashOrderQty	Market buy	Fiat notional to convert
38	OrderQty	Market sell	Base quantity

Optional

Tag	Field	When to Include	Notes
59	TimeInForce	To override default	Market orders default to 3 (IOC)
2362	SelfMatchPreventionID	If enabled	Requires additional permissions
5047	AllocBrokerAccountID	Brokerage clients	IdentityAccountId
50	SenderSubID	Brokerage clients	IdentityId
5074	FundCommissionOption	Brokerage clients

Limit

Set OrdType (40) to 2 (Limit). See Tick Size Requirements, Maximum Notional Order Size By Type, and Limit Orders.

Required

Tag	Field	When to Include	Notes
40	OrdType	Always	2 (Limit)
44	Price	Always	Must meet tick size
38	OrderQty	Always	Base quantity

Conditional

Tag	Field	When to Include	Notes
18	ExecInst	Post-only limit	Set to 6
126	ExpireTime	If TimeInForce = 6	See Time In Force

Optional

Tag	Field	When to Include	Notes
59	TimeInForce	To override default	Limit orders default to 1 (GTC)
2362	SelfMatchPreventionID	If enabled	Requires additional permissions
5047	AllocBrokerAccountID	Brokerage clients	IdentityAccountId
50	SenderSubID	Brokerage clients	IdentityId
5074	FundCommissionOption	Brokerage clients

Stop Market

Set OrdType (40) to 3 (Stop Market). Only sell stop loss orders are supported.

Required

Tag	Field	When to Include	Notes
40	OrdType	Always	3 (Stop Market)
99	StopPx	Always	Stop price
38	OrderQty	Always	Stop Market sell quantity

Conditional

Tag	Field	When to Include	Notes
126	ExpireTime	If TimeInForce = 6	See Time In Force

Optional

Tag	Field	When to Include	Notes
59	TimeInForce	To override default	Stop Market defaults to 1 (GTC)
2362	SelfMatchPreventionID	If enabled	Requires additional permissions
5047	AllocBrokerAccountID	Brokerage clients	IdentityAccountId
50	SenderSubID	Brokerage clients	IdentityId
5074	FundCommissionOption	Brokerage clients

Stop Limit

Set OrdType (40) to 4 (Stop Limit). See Tick Size Requirements.

Required

Tag	Field	When to Include	Notes
40	OrdType	Always	4 (Stop Limit)
44	Price	Always	Must meet tick size
99	StopPx	Always	Stop price
38	OrderQty	Always	Base quantity

Conditional

Tag	Field	When to Include	Notes
126	ExpireTime	If TimeInForce = 6	See Time In Force

Optional

Tag	Field	When to Include	Notes
59	TimeInForce	To override default	Stop Limit defaults to 1 (GTC)
2362	SelfMatchPreventionID	If enabled	Requires additional permissions
5047	AllocBrokerAccountID	Brokerage clients	IdentityAccountId
50	SenderSubID	Brokerage clients	IdentityId
5074	FundCommissionOption	Brokerage clients