Robot Bidding System (English Modern Acol)

Table Of Contents (Show)

Section A: The Uncontested Auction

1. Balance hands

Hands with 4-3-3-3, 4-4-3-2 and 5-3-3-2.

Table Bids and rebids

12-14 HCP
Open 1NT (may include poor 5-card major)
15-16 HCP
Open one of a suit and rebid no trumps at the lowest level
17-18 HCP
Open one of a suit and jump rebid no trumps on the next round
19 HCP
Open one of a suit and jump to 3NT on the next round
20-22 HCP
Open 2NT. Allow slightly unbalanced hands (including a hand with a singleton ace or king).
23-24 HCP
Open 2♣ and rebid no trumps at the lowest level
25-27 HCP
Open 2♣ and rebid 3NT
28-30 HCP
Open 2♣ and rebid 4NT

1.1 Open 1NT

1.1.1 Responses on balanced hands

0-10 HCP
11-12 HCP
With no interest in a 4-4 major suit fit, bid 2♠  (2-way Baron) to invite game. Opener rebids 2NT with a minimum 1NT opening and the lowest 4-card or longer suit with a maximum opening.
13-19 HCP
Raise to 3NT; opener must pass
20-21 HCP
Bid 2♠  (2-way Baron)
22-24 HCP
Raise to 6NT; opener must pass
25+ HCP
Raise to 7NT

1.1.2 Response of 2♣ (Stayman)

no 4-card major
4 heart, possibly 4 spades
4 spades, no 4 hearts

Continuations by responder - weak options (0-10 HCP)

1NT-2♣-2 any-pass
When the object was to play in any suit but club
5-card suit, 4 cards in the other suit
1NT-2♣-2 any-3♣
6+ cards, no major suit fit

Continuations by responder - invitational options (11-12 HCP)

1NT-2♣-2 any-2NT
Invitational, 11-12 HCP, no major suit fit has found
1NT-2♣-2/2♠ -3/3♠
Game invitation

Continuations by responder - strong options (13+ HCP)

1NT-2♣-2 any-3NT No major fit found
1NT-2♣-2/2♠ -4/4♠ Opener must pass
5-card suit, 4 cards in the other major. With 3 cards support, bids to game, otherwise 3NT.
1NT-2♣-2./2♠ -4NT
Quantitative, no major suit fit has been found.

1.1.3 Response of 2 (red suit transfer)

This is a transfer bid, showing at least 5 hearts. Opener rebids 2.

Continuations by responder:

Weak takeout with 5+ cards, 10 HCP or less
5 heats, 4 spades, 11+ HCP. Forcing to at least 2NT. Opener chooses to play in heart, spades or no trumps and whether to bid game.
5 hearts and 11-12 HCP. Invite opener to bid:
- 3 with a minimum and 3+ cards support
- 4 with a maximum and 3+ cards support
- Pass 2NT with a minimum and 2 heats
- 3NT with a maximum and 2 hearts
5 hearts, 4+ cards in the suit bid. Forcing to game with slam interest.
5-card heart suit and the values for game, 13+ HCP. Opener passes with only 2 hearts and correct to 4 if 3+ cards support.
6+ hearts and invites opener to bid 4 with a suitable hand
6+ hearts and the values for game. Opener must pass Transfer Break (1NT-2♦-3♥) shows a 4-card fit for heats and asks responder to go to game with a near maximum, otherwise pass.

1.1.4 Response of 2 (red suit transfer)

A transfer to 2♠, showing at least 5 spades.

Continuations as over 2 response. A no trump rebid by responder shows five spades with balance hand (most likely 5-3-3-2). A spade raise show 6+ cards and a new suit is natural and game forcing.

1.1.5 Response of 2♠  (two-way Baron)

Either: 11-12 with no interest in the majors; or a balance hand with 18+ HCP, usually no 5-card suit; on which slam may be possible in a 4-4 fit.

Opener rebid
Minimum 1NT opening
4+ cards with a maximum opening

Responder rebid:

No further interest.
New suit
Cheapest 4-card suit, game forcing, continuing to investigate fit.
4 cards support for opener's suit, game forcing, no other feature to show.
Jump in new suit
4 cards support, aces of the bid suit (cue bid).

1.1.6 Response of 2NT (minor suit transfer)

A relay to 3♣, show a long minor suit and no interest in game.
Opener rebid 3♣. Responder's responses are:

Weakness take out in clubs.
3 Weakness take out in diamonds.

1.1.7 Response of 3♣/3/3/3♠

All three level responses show strong suits in hands with slam interest.

1.1.8 Response of 4/4♠

Natural, 6+ cards. Opener must pass.

1.2 Balanced hand with 15-19 HCP

Open a 1-level suit and rebid NT. It allows a hand with 5 cards suit.

Rebid NT at the cheapest level
15-16 HCP
Jump rebid NT
17-18 HCP
Jump to 3NT
19 HCP

1.2.1 Responder's continuations after opener rebids in no trumps

After 1NT rebid:
Support opener's suit in 2-level
Weak, 3 cards support.
Support opener's suit in 3-level
Forcing. 3 cards for major and 3+ cards for minor.
Rebid own suit
Weak, 6+ cards.
Jump rebid own suit (3-level)
Invitational, 6+ cards.
New suit in 2-level
Natural and weak, unless it is reverse.
New suit in 3-level Natural and forcing. Something it may have only 3 cards and wait for opener's to show 3 cards support in the first suit (usually major one)

1.3 Opening 2NT

A balanced hand with 20-22 HCP. May have 5 cards suit. It may be on some slightly balance hand (including a hand with singleton ace or king).

1.3.1 Responses to 2NT

Responder should consider whether their side have 25+ HCP for a notrump or major game. Thus 4+ HCP is usually enough for the responder to bid. Any response is then forcing to game.

1.3.2 Responses on balanced hands

0-3 HCP.
4-10 HCP, opener must pass.
3♠ 11-12 HCP, Baron, slam invitation, (See Section 1.3.6)
15-16 HCP, jump to 6NT if minimum else 7NT.
13-14 HCP, balanced hand.
17+ HCP

1.3.3 Response of 3♣ (Stayman)

3 no 4-card major
3/3♠ 5-card suit, implies 4 of the the other major. Opener bids 4/4♠ with 3-card support or 3NT.
no further interest, implies an unbid 4-card major.
3 4 hearts, may have 4 spades
3♠ 4 spades, not 4 hearts

1.3.4 Response of 3 (red suit transfer)

Showing 5+ hears. Opener rebids 3.

New suit
Natural, forcing
5 hearts, otherwise fairly balanced, inviting opener to choose between 3NT and 4.
4 To play, shows 6+ hearts.
Invitational, 5 hearts, about 11-12 HCP. Transfer Break

May be use if opener's hand is so improved by the transfer as to make game likely opposite six small hearts and a worthless hand. E.g. 2NT-3-4.

1.3.5 Response of 3

Transfer to 3♠, showing 5+ spades. Continuations as over 2NT-3.

1.3.6 Response of 3♠ (Baron)

Fair balanced hand with slam interest (a good 10+ HCP), to find out if the opener is minimum or maximum and if there are 4-4 fit.

Opener rebids
With a minimum opening
Lowest 4-card or longer suit
With a maximum opening

Responder rebids
Pass 3NT
No further interest in slam
The cheapest 4-card or longer suit
Opener continues to show 4-card;
But 4NT by either partner is natural and may be passed.

The partnership is always forced to slam if opener shows a maximum over 3♠.

2. Unbalanced hands

2.1 Open bids of one of a suit

Choice of suit to open (if 1NT is not suitable)

Open hand requirements:

2.1.1 Upper Limit

The normal range for 1-level suit opening is 12-19 HCP. For stronger hands with distribution consideration, they may be downgrade to 1-level suit opening.

2.2 Raising the opening bid

2.2.1 Support partner's opening bid in a major whenever you have 4+ cards in that suit

Using LTC (Losing Trick Count) for major raise:

A major raise to two level allows three cards with good distribution. For three level or higher, 4+ cards is a must.

2.2.2 Splinter and pudding raises

Over 1s, bids of 4♣, 4 and 4 show 4-card support, game values (11-15 HCP) and a singleton or void  in the bid suit.

Over 1h, the splinter bid are 3♠, 4♣ and 4.

Hands worth a raise to game because of their point count, say 12-15 HCP, but which have no interesting in distributional features (shortages or long suits) can go through 3NT. The loss of a natural 3NT response should be noted.

2.2.3 Very good raise

With 16+ HCP and 4+ cards, make a jump shift response before supporting the opener's suit (See section 2.3.2). With less than 16 HCP, always raise partner immediately. When holding a game going hand, only bid a new suit by jump to game with 3-card support.

2.3 Responding in a new suit

For 1-level, it is 6+ HCP, 2-level, it is 9+ HCP and 4+ cards. It forces one round if the responder has never passed. For 1♠-2, it needs 5+ cards.

2.5 Opener's second bid

2.5.1 Opener's options with a weak unbalanced hand (in order of preference)

2.5.2 With a stronger unbalance hand
Jump in suit opened
16-18 HCP, 6+ strong card (non-forcing after 1-level response, forcing after 2-level).
For stronger hand, one can jump to game (may be strong 2 opening is more appropriate).
Jump support partner's suit
16-18 HCP, 4+ cards.
Jump in new suit
4+ cards (19+ HCP after 1-level response, 16-19 HCP after 2-level), game forcing.
The first bid suit usually has 5+ cards, except for 4-4-4-1 case.
16+ HCP, 4+ cards, 1 round forcing.
The first bid suit usually has 5+ cards, except for 4-4-4-1 case.

2.6 Responder's second bid

After opener rebids a third suit without a reverse or jump:

With a weak hand (6-9 HCP)

With invitational hand (10-12 HCP)

With a game hand (13+ HCP)

2.9 Strong two opening bids

2.9.1 Opening
2/2/2♠ At least 8 playing tricks. Force 1 round with 2 defensive tricks. Rule 25 applies. (HCP + length of longest suit + length of second longest suit >= 25)

2.9 Response
Negative, 0-7 HCP
Opener rebids
1. Rebid same suit: natural.
2. New suit: 4+ cards, forcing 1 round.
Single raise
4-7 HCP, 3+ cards with an ace OR
8+ HCP, with 3+ cards
Double raise
3-7 HCP, 4+ cards with 2 kings or 1 kings and shortage
New suit
8+ HCP, decent 5+ cards OR 12+ HCP with 4+ cards
Jump new suit
8+ HCP, solid 6+ cards
8-11 HCP, balanced hand, not support partner suit, stopper in other suits. Without stoppers, bid 2NT then 3NT
Except 2NT, other responses are natural and forcing to game.

Section B: Dealing with intervention

1. Takeout doubles of overcalls after partner has opened

1.3  Negative double

A double promises 4 cards in any unbid major suit. Eg.

1♣-(1♠)-X Promises 4 hearts
Promises exactly 4 spades
1♣-(1)-1♠ Show 5+ spades as double would show 4
1♣-(1)-X Shows 4-4 in majors

Section C: Defensive Bidding

5. Defense to opponent's opening 1NT

Penalties, 16+ HCP, balanced hand, a little less if  one has a very promising lead..The doubler's partner is usually pass except for a very shapely hand. A new suit at the two level is very weak, at three level it is not forcing but encouraging. If opener's partner rescues into a suit, any further doubles are also for penalties. 6+ HCP with 4 trumps headed by a honour are quite adequate.
10+ HCP, preferably 6 cards (may be good 5 cards, with 5-4-2-1).
Jump Overcall
10+ HCP, 7 cards or very good 6 cards with 7 winning tricks
Landry. 8-15 HCP, at least 5-4 in major (the better the shape, the fewer the points required). With a limited hand, responder show the better major or, with equal length, bids 2, to invite the overcaller to choose between major. With a good fit, responder may jump to 3, 3♠ , 4 or 4♠.


  1. Bidding other that those listed in the page may not be implemented for the robot.
  2. The page will be updated after robot has been modified and tested to be stable.
  3. The system is mainly based on the booklet "Standard English Modern ACOL" copyrighted by the English Bridge Union.

Last modified at 4-Feb-2022 by WeWeWeb.